Performance · Troubleshooting guide
My PC Is Running Very Slowly: A Complete Step-by-Step Guide
Covers Windows 10/11, macOS and Linux · a long guide, about 20 minutes to work through
A slow computer is a symptom, not a diagnosis. It tells you that something is taking longer than it should — but not what, or why. In practice, "slow" almost always comes from a short list of places: too much demand on the CPU, not enough memory, a storage drive that is full or failing, heat that forces the machine to slow itself down, or a program quietly hogging resources in the background.
This guide walks through twenty of those causes in the order a technician would check them. The method is the same every time: look at the evidence, make one safe change, and test before moving on. Nothing here asks you to install a "cleaner" or a magic booster. If a fix needs a command or a system setting, it says what that does, what could go wrong, and when to stop and get help. Work from the top down — most machines are noticeably faster within the first five or six sections.
Quick reference
Use this table to jump straight to the most likely section. "Risk" tells you how invasive the first check is, so you can start with the safe ones.
| Symptom | Likely cause | First check | Risk |
|---|---|---|---|
| CPU pegged near 100% | One process working hard, or malware | Resource usage | Low |
| Memory nearly full | Too many apps / browser tabs | RAM | Low |
| Disk stuck near 100% | Full drive, update, or failing drive | Storage | Low–Med |
| Very slow to start up | Startup load, full or old drive | Startup | Low |
| Browser slow, desktop fine | Tabs, extensions, or network | Browser | Low |
| Whole system freezes | RAM, heat, or a failing disk | RAM, Heat | Med |
| Fan constantly loud | Dust, high load, or a failing fan | Overheating | Low |
| Slower after running a while | Thermal throttling, background app | Overheating | Low |
| Slow only when online | A network issue, not the PC | Network | Low |
| Slow after installing something | A new app, driver, or update | Recent change | Low |
Start here
If you're not sure where to begin, follow these nine steps in order. Each one is cheap to do, and together they rule out most causes before you touch anything advanced.
- Identify the symptom. Is it always slow, or only when doing one specific thing? Note when it started.
- Check CPU, memory and disk usage while it feels slow — this is your baseline. See section 1.
- Look at startup programs and switch off what you don't need. See section 2.
- Check available storage and clear the safe stuff. See section 4.
- Check temperatures and fan noise — especially if it's a laptop. See section 11.
- Note any recent changes — installs, updates, new hardware. See section 18.
- Run a security scan with your existing, reputable tool. See section 9.
- Make one change, then test. Don't change several things at once.
- Go deeper only if needed — clean boot, disk repair, or a reinstall. See section 19 and section 20.
Diagnostic checklist
Tick the symptoms that match your machine. The suggestions below point you at the most likely sections to check first. This is a starting point, not a hardware test — it just helps you skip the sections that probably don't apply.
Tick at least one symptom to see suggested sections.
The diagnostic path: check each stage, and the one that is at its limit is usually your bottleneck.
Find out what is actually making your PC slow
A slow machine can feel the same whether the cause is a misbehaving program, a full disk, or heat. That is exactly why the first step is to measure rather than guess. Open your system's built-in performance monitor and watch what happens while the machine feels slow — not while it is idle. You are looking for which resource is near its limit: the CPU (processing), memory (RAM), disk, GPU, or network. Whatever is sitting at or near 100% while you experience the slowness is your best first clue.
Before you change anything, spend a minute or two here. Note the usual numbers, and what spikes when the problem appears. That baseline is what tells you later whether a fix actually worked. On Windows, press Ctrl+Shift+Esc to open Task Manager: the Performance tab shows live usage and the Processes tab shows which program owns it. On macOS, open Activity Monitor (from the Utilities folder or via Spotlight). On Linux, top or htop in a terminal does the job — the exact command can vary by distribution.
| Resource | What sustained high usage can mean | Where to check |
|---|---|---|
| CPU | A program working hard, an update, or malware | Task Manager / Activity Monitor → Processes |
| Memory (RAM) | Too many apps open, or not enough RAM installed | Performance → Memory; the "what's using it" list |
| Disk | A full drive, an update, a file-system check, or a failing drive | Free storage space; disk health (SMART) |
| GPU | Heavy graphics, a stuck video process, or a driver issue | Task Manager GPU column / Activity Monitor |
| Network | Sync or download activity, or a slow, contended connection | Network usage; test a local task vs an online one |
Too many programs running at startup
Every program you tell your computer to launch at sign-in runs in the background the moment you log in, whether you use it or not. Individually these apps are small, but together they can cost you minutes at boot and a steady slice of memory all day long. This is one of the most common causes — and one of the safest to fix, because turning an app off at startup does not uninstall it. You can still open it manually whenever you want.
How to manage startup programs, by platform
Windows 10/11 — Open Task Manager, go to the Startup apps tab, and set items you don't need to Disabled. You can also check Settings → Apps → Startup.
macOS — Go to System Settings → General → Login Items, and remove apps from the "Open at login" list. Also check "Allow in the background" for the items listed below it.
Linux — Most desktops have a "Startup Applications" list in settings. Autostart entries also live in ~/.config/autostart. The exact menu name varies by desktop environment.
The rule of thumb: keep the things you genuinely need automatically (your security software, and any backup or sync tool you rely on), and switch off the rest — game launchers, chat apps, media players, vendor "toolbars", and duplicate utilities. If you're unsure whether an item is safe to disable, a quick search of its name is usually enough. If turning a few off doesn't change boot time, startup wasn't your main cause and you can move on.
| Program type | Usually safe to disable at startup? | Notes |
|---|---|---|
| Security / antivirus | No | Let it stay active in the background |
| Backup or sync you rely on | Usually yes | You lose automatic syncing; start it on demand |
| Game or app launchers | Yes | Open them when you want to use them |
| Chat / messaging apps | Yes | Start them on demand |
| Vendor "boosters", toolbars, utilities | Yes | Often unnecessary, sometimes unwanted |
| Two tools from the same vendor | Yes — keep one | Running both can conflict |
Not enough RAM (memory pressure)
Memory pressure is a classic cause of slowness. When the apps you have open need more RAM than is installed, the system starts borrowing from the storage drive — called paging or swap. Because a drive is far slower than RAM, everything feels heavy and laggy, especially when switching between programs. If memory is consistently pinned near its maximum while you work, that is a real signal.
It is worth being careful here, because high RAM usage is not automatically a fault. Modern operating systems fill spare RAM with recently used data so it is instantly available again. A memory meter sitting at 70–80% while the computer runs smoothly is normal, not a problem. The difference is whether the machine is actually sluggish and whether the "in use" figure stays stuck at the ceiling with almost nothing free.
If it is, closing unneeded browser tabs and background apps is the first fix, and adding RAM is the real one — but only when your typical workload (dozens of tabs, virtual machines, video editing) genuinely exceeds what's installed. Upgrading RAM is usually a cheap and safe change on a desktop, and often a big one on an older machine. It's also one of the few upgrades that helps immediately and permanently, with no software involved.
Your storage drive is nearly full
An almost-full drive hurts performance more than people expect. Operating systems and many programs need free space to work — for temporary files, for swap when memory runs low, and for the room to rewrite data in place. When a drive is nearly full, all of that gets slower, and on older hard drives the effect is especially noticeable. A drive with less than roughly 10–15% free space is a reasonable threshold to start clearing.
Begin with the safe, reversible cleanups: empty the Recycle Bin or Trash, delete large downloads you've finished with, and let the system remove temporary files (Windows' Storage Sense or Disk Cleanup, and macOS' Storage manager, all do this). One caution: avoid deleting files just because they look large or unfamiliar — some big folders are part of how the system works, and removing the wrong one can cause real problems. Freeing space is low-risk and often helps, but it treats a contributing factor rather than a failing component.
| Situation | Recommended action | Risk |
|---|---|---|
| Under ~10% free space | Clear temp files, downloads, and the bin | Low |
| Large finished downloads | Delete or move them to another drive | Low |
| Full because the drive is small | Add or replace with a larger (or SSD) drive | Low–Med |
| A big folder you don't recognise | Leave it — check before deleting | Medium |
Hard drive vs SSD: your drive type matters
If your computer uses a traditional spinning hard drive (HDD) rather than a solid-state drive (SSD), that alone can explain a great deal of the slowness. HDDs are mechanically limited — they must physically spin up and move a read head — so booting, opening programs, and loading files all take noticeably longer than on an SSD. A healthy HDD can still be "fast enough", but if your machine runs a modern operating system with lots of background activity, an SSD is the single upgrade that most often makes an old PC feel new again.
That said, don't assume every slow computer needs an SSD. If your machine already has one, or if your measurements show the drive is rarely the bottleneck, this won't be your answer. It is also worth checking the drive's health first (covered in section 15), because a failing drive is slow for a different reason than a simply old one.
If you do consider an SSD, know that it is usually a straightforward change — your data can be cloned across or the system reinstalled — and it is one of the higher-value upgrades available. On a very old system with other limits, though, weigh the cost of the upgrade against the value of the whole machine.
Background apps and resource-heavy processes
Beyond startup items, plenty of software runs quietly in the background and can quietly consume resources: cloud-sync clients (photo, file or document sync), game and app launchers, updaters, real-time antivirus scanning, and browsers with many processes. Any of these can show up as a steady load on CPU, memory or disk. The key is to look at the process list while the machine is slow and match the heavy process to a program you actually recognise.
Most heavy processes are completely legitimate. A burst of disk activity can be an update or a sync client working through a batch of files; a spike in CPU can be an indexer or a scheduled scan. Those are normal and usually pass on their own. What you're watching for is the process that stays high for a long time with no obvious reason, or one with a name you don't recognise. If you can't identify a process, a quick search of its exact name — or of its file path — is the safe way to check. If it turns out to have nothing to do with your computer, that points toward malware, which has its own section below.
Windows Updates, macOS Updates, and system software
Operating systems are large, and updating them is one of the most resource-heavy things a computer does. Right after an update — and during the hours that follow — a system can be slower than usual while it applies changes, rebuilds search indexes, and finishes background tasks. This is temporary and usually resolves on its own within a day or so, sometimes only after a restart you'd skipped. If your PC got slow shortly after an update, patience plus a restart is often the whole answer.
The important caveat: updates should not be disabled to fix slowness. Staying current matters for security and for many bug fixes, and an update that lands and then causes a problem is better addressed than avoided. If performance clearly got worse right after a specific update and stays that way, look at what that update touched — a new driver, a setting, or a feature you can switch off — and fix that specific change rather than leaving the system unpatched. On both Windows and macOS you can generally see recent update history and, in some cases, uninstall a particular update that misbehaved.
Outdated, broken, or conflicting drivers
Drivers are the small pieces of software that let the operating system talk to your hardware. A graphics driver, a storage controller driver, or a chipset driver that is outdated, corrupted, or the wrong version can cause stuttering, random slowness, or one particular task feeling heavy while the rest of the system is fine. If the slowness is tied to a specific activity — video playback, games, using a particular device — a driver is a strong suspect.
The safe sources for drivers are the operating system's own update mechanism and the manufacturer — the chip or device maker, or the PC/laptop vendor's support page. Please avoid random third-party "driver updater" utilities and unofficial driver download sites; they are a common way to install the wrong driver, or worse, unwanted software.
If a driver update made things worse, both Windows and macOS offer a way to roll back to the previous driver, which is usually far safer than hunting for a "perfect" version by hand. On Windows, Device Manager is where you see driver status and warnings; on macOS, the system reports show it. If you're not comfortable with driver rollbacks, this is a reasonable place to bring in a technician.
Malware, adware, and unwanted software
Malware and adware are worth checking simply because their symptoms overlap so much with ordinary slowness: unexpected CPU or network use, new pop-ups, a browser that has changed its search engine or homepage, or programs you don't remember installing. Modern malware is often quiet rather than dramatic, so "the computer feels off" is a legitimate reason to look. The goal of this step is to check, not to panic — most machines that feel slow are not compromised.
Use what you already have. Windows ships with Windows Security (Defender), a reputable free scanner; run a full scan rather than just a quick one, and let it finish without heavy use. macOS has built-in protection, and adding a reputable scanner is a fine way to get a second opinion. Linux systems are less commonly targeted, but a full system check plus a look for unexpected startup items is still sensible.
The main thing to avoid is "anti-malware" or "PC repair" software that arrived by itself or by aggressive pop-ups. That is very often the problem, not the solution — and you should not switch off your real security software as a routine part of troubleshooting. If a scan finds something it can remove, let it, then restart and re-check your baseline from section 1.
Your browser and too many tabs
Browsers are among the heaviest normal applications on a computer, and a lot of "my PC is slow" is really "my browser is slow". Each tab and each extension uses memory; a browser with dozens of tabs can use several gigabytes of RAM, and a misbehaving or ad-injecting extension can add CPU load on every single page. If the desktop feels fine but the browser drags, start here before touching the system.
Begin with the cheap tests. Close the tabs you aren't actively using, then open a fresh private or incognito window. If a site loads normally there, the difference is almost certainly an extension or cached data. Disable extensions in groups (or use a clean profile) to find the culprit, clear the browser cache if things feel stale, and consider toggling the browser's hardware-acceleration setting if you see stuttering in video or scrolling.
Resetting the browser's settings — which keeps your bookmarks but clears extensions and preferences — is a reasonable final step for that app. Because it is confined to the browser, it is low-risk to the rest of your computer, and it is quick to undo if it doesn't help.
Overheating and thermal throttling
When a CPU or GPU gets too hot, it deliberately slows itself down to stay within safe temperatures. This is called thermal throttling, and it protects the hardware at the cost of performance. The tell-tale pattern is a computer that runs fine at first and then gets slower the longer it has been on, often with a fan that is noticeably loud or spinning at full speed. Laptops are especially prone, because their cooling is compact and easy to block.
The usual physical causes are dust clogging the vents and fans, dried-out thermal paste on an older machine, or simply using a laptop on a soft surface that blocks its air intake. Safe things you can do: keep vents clear, use the device on a hard flat surface, and gently clean accessible dust with compressed air while the machine is off and cool. If the machine is old, the thermal paste is likely dry, or the fan is physically struggling, that is a job for a proper clean or service — not something to keep pushing.
The figures below are rough. Real safe temperatures vary a lot by hardware design, so treat them as general guidance, not hard limits.
| Approx. CPU under load | Rough reading | What to do |
|---|---|---|
| Up to ~70°C | Comfortable | Nothing needed |
| ~70–90°C | Warm, but common under load | Keep vents clear; monitor it |
| ~90°C and up, sustained | Likely throttling / overheating | Clean dust; check the fan; service if old |
Power settings and performance modes
Power settings quietly change how hard your computer works. A battery-saver or "best efficiency" mode tells the system to hold back — lowering clock speeds and background activity — to stretch the battery, and that can feel like slowness even when nothing is wrong. On a laptop running on battery this is expected behaviour, and it is why a machine often feels noticeably faster when it is plugged in. On a desktop, a power plan set to save energy can have a similar, if milder, effect.
The right setting depends on what you value, not on the idea that "faster is always better". For everyday use, a balanced mode is usually the sweet spot. A maximum-performance mode can help a desktop under real load, but it uses more power and produces more heat for little benefit in normal tasks — and on a laptop it will cut battery life. A quick, informative test: if you have been running on battery, plug the machine in and see whether it feels faster. If it does, power management is part of your problem, and the fix is a setting, not a component.
Too many installed programs and unnecessary services
Over time a computer accumulates software: trial apps you forgot, games you no longer play, and — most relevant to performance — a lot of small background helpers. Many installed programs add auto-start items, updaters, or "services" that keep running even when you are not using the app itself. Individually they are small, but a dozen of them add up to real background load, and removing the ones you don't use is a safe, permanent win.
The safe approach is to uninstall whole programs you no longer want, using the normal Remove apps (Windows) or Applications (macOS) flow. Resist the temptation to hunt through and delete individual files or services by hand — blindly removing things from a services list or from program folders can break the system. A practical method: work out what you actually use, uninstall the rest, and then revisit startup items (section 2) to switch off any leftovers. Done this way, it tidies the machine without touching the operating system.
Corrupted system files or operating-system problems
Occasionally the slowness comes from the operating system itself — a corrupted system file, a damaged component, or a setting that has gone wrong. The good news is that both Windows and macOS ship built-in tools to check and repair their own core files, and these are designed to be safe to run. It is worth letting the system verify itself before reaching for anything more invasive.
System-file repair commands, explained
Windows — Two built-in commands do the job. DISM /Online /Cleanup-Image /RestoreHealth repairs the component store that Windows draws files from, and sfc /scannow (the System File Checker) scans protected system files and replaces any that are damaged. Run them in that order. Both need an administrator PowerShell or Command Prompt, both are non-destructive (they check and repair, they don't touch your files), and both can take a while and may ask for a restart.
macOS — Run First Aid in the Disk Utility app to verify and repair disks and file systems. For deeper checks, restart into Recovery (hold the power button on Apple silicon, or Cmd+R on Intel) and use its utilities.
Linux — The tools differ by distribution and by whether you use ext4, btrfs, etc. Generally this means a file-system check (often fsck run from outside the mounted system) and a package-manager repair. Check your distribution's documentation rather than assuming one universal command.
DISM /Online /Cleanup-Image /RestoreHealth
sfc /scannowThese commands are safe and reversible, but they can run for tens of minutes and may restart the machine — so run them when you have time. If they report that they repaired something, that may well have been your problem. If they find nothing, the cause is elsewhere in this list.
Storage health and drive errors
A drive that is beginning to fail often gets slow before it fails outright. As sectors wear out, the drive spends more time retrying reads and writes, and the whole system feels sluggish — sometimes with stutters, the occasional freeze, or files that suddenly won't open. This is a different problem from a drive being full or old: here the component is degrading, and no amount of software cleanup will permanently fix it.
The concept to know is SMART, a set of health sensors built into most modern drives that report things like reallocated (repaired) sectors and read-error rates. You can read these with the drive's own tools or reputable disk-utility software, and your operating system may warn you directly if a drive is failing. Repeated file-system errors on the same drive are another red flag.
Back up first. If there is any sign of a failing drive, copy your important data somewhere safe before attempting any repair. Some repairs (a file-system check, for example) are safe, but if the drive is physically failing the right move is usually replacement rather than repeated repair attempts. A new drive is also a good moment to move to an SSD if you don't already have one.
chkdsk C: /fchkdsk checks the file system and fixes errors; on the drive Windows is installed on it runs at the next restart. It is generally safe, but because it works directly on the disk, it is the kind of step where a fresh backup is cheap insurance. On macOS, Disk Utility's First Aid does a similar check without the restart.
Aging hardware limits
Sometimes the honest answer is that the hardware has simply reached the end of its comfortable life. A CPU from a decade ago, four gigabytes of RAM, a small spinning drive, and integrated graphics were fine when bought, but they struggle with the size and background activity of current software. When the measurements from section 1 show resources maxed out during perfectly normal use — and the machine is old — that is a hardware limitation, not a bug to fix.
The useful question is whether upgrading is worthwhile. Adding RAM or an SSD can extend an otherwise good machine's life for a modest cost, and that is usually worth doing. But if the processor itself is the limit, no amount of extra RAM or storage will make it fast — at that point you are comparing the cost of upgrades against buying a newer machine.
The key distinction is between a slow but healthy PC and a slow because something is failing PC. The first is a decision about value; the second is a decision about repair. The diagnostics above are what tell you which one you have, and that makes the decision much easier to make.
A slow network that feels like a slow PC
One of the most common misdiagnoses is treating a slow internet connection as a slow computer. If the machine feels slow specifically when online — websites take a while to load, cloud apps are laggy, downloads crawl — but local tasks (opening files, typing, switching apps) are quick, the bottleneck is probably the network, not the PC. Sorting this out saves you from chasing the wrong cause entirely.
The quick way to isolate it: do a purely local task and an online task back to back. If the local one is snappy and the online one is slow, look at the network. Check whether other devices on the same connection are affected — if they are, it is the connection or the router, not your PC. Try a different Wi-Fi channel, move closer to the router, or test a wired connection if you have one. Simple tools can show the round-trip time (latency) to a known address; a high or spiky number points at the network path.
ping 1.1.1.1
tracert 1.1.1.1If the problem is the connection, the fixes are on the router or provider side, and no amount of PC tuning will change it. Recognising that boundary is itself the fix.
Something you changed recently
When a computer that was fine suddenly gets slow, the single most valuable question is: what changed? A new application, a driver update, an operating-system update, a newly connected peripheral, newly installed RAM or a drive, or even a settings change can all be the trigger. Slowness that began at a specific point in time is a strong clue, because it narrows the cause to whatever was introduced around then.
Work the change history backwards. Think about the last day or week: what did you install, update, connect, or change? Then try reversing the most likely item — uninstall the new app, roll back the driver, disconnect the peripheral, or (on Windows) look at recent updates if a specific one is the suspect. Changing or removing one thing at a time, and testing after each, is what tells you which change was responsible.
This approach is fast and safe, because it only undoes recent additions. It frequently solves "it was fine until yesterday" problems without any deep troubleshooting at all, which is exactly why it is worth doing before you move on to the heavier steps.
Clean boot and advanced isolation
If the obvious causes are ruled out and the machine is still slow, the next level is to isolate third-party software from the operating system. The idea is a "clean boot": start the system with the minimum of background programs and services, so that if it runs fast in that stripped-down state, a piece of software you re-enable is the cause. This is a genuinely useful diagnostic, but it is the first step that touches system startup more directly, so do it deliberately and know how to reverse it.
On Windows, the classic method is the System Configuration tool (msconfig) combined with disabling non-Microsoft services, plus switching off startup items, then rebooting; you re-enable things in groups to find the offender. On macOS, the equivalent is managing Login Items and Launch Agents. The discipline that matters is the one-change-at-a-time rule: change one thing, restart, test; if it's still slow, change the next.
Do not leave the machine in a stripped-down state longer than you need to, and do not disable security software or core services. If you are not confident, or the machine behaves oddly in safe or clean mode, that is a point to stop and consider professional help rather than pushing deeper. These steps are powerful but entirely optional — many slow computers are fully resolved without ever reaching here.
| Action | Risk level | Back up first? |
|---|---|---|
| Disable startup items | Low | No |
| Clean boot with System Configuration | Low (reversible) | No — but know how to reset |
| Disable non-Microsoft services | Medium | Good idea |
| System-file repair (sfc / DISM) | Low | No (non-destructive) |
| File-system check (chkdsk) | Low–Medium | Yes, recommended |
| Reinstall the operating system | High | Yes, essential |
When it's still slow: final diagnosis and next steps
If you have worked through the list and the computer is still slow, the last job is to combine what you have found into a decision. Look back at the evidence: which resource was maxed out, is the drive healthy, is the machine hot, is it old, and did anything change recently? The pattern points to one of a few outcomes, and matching your observations to them is the whole point of having measured along the way.
| Observation | Most likely explanation | Next step |
|---|---|---|
| Resources maxed during normal use; machine is old | Hardware limits | Upgrade RAM/SSD, or replace the PC |
| Drive-health warnings or frequent stutters | A failing drive | Back up now, then replace the drive |
| Hot, loud fan, slower over time | Overheating / throttling | Clean or service the cooling |
| Slow only when online | The network, not the PC | Check the router / connection |
| Fine until a specific install or update | That change | Undo the change |
| Slow but no hardware fault; messy system | Software bloat | Clean install (after a full backup) |
The important thing at this stage is to separate slow but healthy from slow because something is failing. A machine that is simply out of its depth (an old CPU, not enough RAM for your workload) is a value decision — upgrade a component, replace the PC, or accept it for lighter use. A machine where a component is degrading (a failing drive, chronic overheating) is a repair-or-replace decision, and backing up first is non-negotiable. Reinstalling the operating system is a legitimate final step for a system that is software-messy but has healthy hardware — but it is only justified once you have ruled out the hardware, and it erases the system drive, so it always comes after a full backup. If you are unsure which box you are in, that is exactly when a technician is worth the call.
When to stop troubleshooting
Troubleshooting has a point of diminishing returns, and knowing it is part of doing it well. Here is when to stop adjusting settings and move to a concrete action:
- Back up your files now — the moment you suspect a failing drive, repeated freezes, or any hardware fault.
- Replace the storage if disk health (SMART) reports failure, or if you see frequent stutters and read errors.
- Upgrade RAM if memory is consistently pinned and your workload genuinely needs more.
- Have it cleaned or serviced if it is hot, the fan is loud, or it is an older laptop with dry thermal paste.
- Consider replacing an aging PC if the CPU itself is the limit and upgrades would cost close to a new machine.
- Reinstall the operating system only after you have ruled out hardware, and only after a full backup.
- Call a repair technician if you are unsure, if safe-mode/clean-boot behaves oddly, or if a component may be failing.
Final checklist
A compact version you can print or keep beside you while you work.