How To Fix A Slow Computer
A practical step-by-step guide to how to fix a slow computer, including preparation, instructions, common issues, tips, and next steps.
How To Fix A Slow Computer
A slow computer usually comes from too many startup programs, not enough storage space, or background tasks you cannot see. This guide shows you how to speed up your PC in about an hour using tools already built into Windows, so you can avoid paying for repairs or replacing a machine that still has life in it. The most important rule is to restart your computer before you start any optimisation work, because many slowdowns are simply temporary glitches that clear themselves.
Fast Answer
- Restart first: Clears temporary memory and stops background tasks.
- Disable startup apps: Open Task Manager and turn off the heavy ones.
Before You Start
- A Windows 10 or Windows 11 computer with admin access
- At least 30 minutes of uninterrupted time
- An external hard drive, USB stick, or cloud storage for backups if you plan to clean files
- A stable internet connection if you plan to run Windows Update or check for driver updates
- Your Microsoft account password or PIN for settings changes
Step-by-Step Instructions
Restart Your Computer Completely
Click the Start button, then select Power and choose Restart. Do not use Shut Down and turn it back on manually, because Windows Fast Startup can keep kernel memory from clearing. A full restart closes every background process, releases locked files, and resets memory that may have become fragmented over days or weeks.
After the restart, give the computer two or three minutes to settle before you judge its speed. Antivirus scans, update checks, and cloud sync often run in the first minutes after boot, so the machine may feel slower before it gets faster.
Disable Heavy Startup Programs
Press Ctrl + Shift + Esc to open Task Manager, then click the Startup apps tab. You will see a list of programs that launch automatically when Windows starts, each labelled with a startup impact rating: Low, Medium, or High.
Right-click any program with a High impact that you do not need immediately after boot, and select Disable. Common examples include music tools, messaging apps, updaters for PDF readers, and cloud storage clients you can open manually later. Do not disable your antivirus software or core Windows processes, because that can leave your system unprotected or unstable.
Restart your computer again and check whether the boot time and general responsiveness improve. You can always re-enable any disabled program later by returning to the same list.
Free Up Storage Space With Storage Sense
Open Settings, select System, then choose Storage. In Windows 11, turn on the Storage Sense toggle so your PC automatically removes temporary files, recycle bin items older than 30 days, and downloads folder content you have not touched. In Windows 10, the feature sits in the same location under the name Free up space now.
Call your PC should have at least 15% of its total storage free to run smoothly. If you have a 256 GB hard drive, that means keeping roughly 38 GB empty. When the drive fills to capacity, Windows struggles to write temporary files, and every application slows down.
If you are still low on space, review your Downloads folder and delete large files you no longer need. Check your Recycle Bin and empty it if it contains many files, then uninstall any applications you have not used in the past six months through Settings, Apps, then Installed apps.
Run Disk Cleanup on Legacy Files
Type Disk Cleanup in the Windows search bar and open the desktop app. Select your main drive (usually C:) and press OK. The tool calculates how much space you can recover and shows categories such as Windows Update Cleanup, Temporary Internet Files, and Thumbnails.
Check the boxes for Temporary files and Windows Update Cleanup if that option appears, then click Clean up system files. The scan runs again to include system-level data, and this second pass often finds significantly more junk than the first one.
Click OK to begin deletion. This tool is safe to use, but confirm you have no important files inside the folders it targets, especially the Downloads folder if you selected it.
Run the Built-In Disk Defragmenter on Hard Drives
If your PC has an older mechanical hard drive (not an SSD), files become fragmented over time as Windows writes data to scattered sections of the platter. Search for Defragment and Optimize Drives, open the app, then select your hard drive and click Optimize.
Do not run this tool on a Solid State Drive (SSD). SSDs have no moving parts and do not benefit from defragmentation; the process only writes extra data and shortens the lifespan of the drive. Windows automatically schedules optimisation for most drives, so this step is mainly for older machines where automatic schedules have been disabled.
If you are unsure which type of drive you have, go to Settings, System, Storage, then Advanced storage options and Disks and volumes. The drive type is listed there, and the defragmenter app itself marks SSDs as Solid State Drive.
Check for Background Processes Draining Resources
Open Task Manager again and click the Processes tab. Click the CPU column header to sort processes from highest to lowest usage, then inspect any process that shows sustained high usage above 30% for more than a few minutes.
If a program you recognise is using high CPU, close it from inside the app itself. If a process has an unfamiliar name, right-click it and choose Search online to check whether it is legitimate software or malware before you end it. Malware such as cryptocurrency miners and adware routinely drain CPU and slow down computers while hiding behind innocent-looking names.
You can end a suspicious task with the End Task button, but do this only after you have verified the name online. If your machine continues to slow down even when idle, run a full antivirus scan with Windows Security, which is already built into Windows 10 and 11.
Install Windows Updates
Open Settings, select Windows Update, and click Check for updates if the status does not already say You are up to date. Windows updates include security fixes, driver improvements, and performance patches that can resolve slowdowns caused by bugs in previous versions.
If updates are pending, install them and restart your computer. Some updates take longer than others; plan for up to an hour if there are many pending. After the restart, return to Windows Update and confirm there are no more optional updates available, particularly for graphics drivers and chipset drivers, which directly affect system responsiveness.
If you are on an older machine, avoid the Windows 11 upgrade if Microsoft's health check app says it is not fully compatible. Running unsupported hardware can cause more problems than the speed improvements are worth.
Adjust Visual Effects for Maximum Performance
Type Performance in the Windows search bar and open Adjust the appearance and performance of Windows. Under the Visual Effects tab, select the radio button for Adjust for best performance. This disables animations, transparency effects, and shadow rendering that consume memory and CPU cycles.
This setting makes Windows look flatter and less polished, but it frees up resources for your actual work. If the plain look is too jarring, select Custom and keep only Show thumbnails instead of icons and Smooth edges of screen fonts checked. Those two options preserve most of the visual quality while cutting most of the overhead.
Click Apply, then OK. The change takes effect immediately, and you will notice snappier response when switching between windows and opening menus.
Reset the PC as a Last Resort
If your computer remains slow after every other step, Windows can reinstall itself through the Reset this PC feature. Go to Settings, System, Recovery, then Reset this PC. Choose Keep my files to preserve your personal documents while removing installed applications and resetting system settings.
This process takes 30 to 90 minutes, rewrites the operating system core, and fixes deep corruption that manual cleanups cannot reach. Back up any files you have not already saved to an external drive, because although the Keep my files option preserves personal data, unexpected errors during reset can still cause loss.
After the reset finishes, you will need to reinstall your applications, sign in to accounts, and reconfigure settings. This is the most invasive fix, use it only after you have tried everything else.
Quick Reference
| Situation | Use this | Why |
|---|---|---|
| Boot takes minutes | Disable startup apps | Fewer programs load at launch, so the desktop appears faster |
| Full hard drive | Storage Sense or Disk Cleanup | Windows needs free space for temporary files and caching |
| System sluggish during file access | Defragment HDD only | Consolidates file fragments for faster reads on mechanical drives |
| Programs freeze randomly | Check Task Manager and end suspicious processes | Frees CPU and catches potential malware early |
| Slow after Windows updates | Check for more updates or reset | Driver mismatches and corrupted system files need repair |
Final Checklist for Fixing a Slow Computer
- I have restarted my computer and tested its speed after a clean boot.
- I have disabled at least the high-impact startup programs in Task Manager.
- I have freed up at least 15% of my main drive using Storage Sense or Disk Cleanup.
- I have defragmented my hard drive, or confirmed my SSD does not need it.
- I have checked Task Manager for suspicious background processes and run a full antivirus scan using Windows Security.
- I have installed all pending Windows updates and restarted again.
- I have adjusted visual effects for performance, or I have decided the visual trade-off is not worth it.
- I have backed up my files so I can use Reset this PC if the slowdown persists.
Common Problems When You Fix a Slow Computer
- The computer is still slow after restarting. If restarting does not help, you likely have too many startup programs or a nearly full drive. Move straight to the Task Manager step and the storage cleanup step before trying anything more radical.
- You cannot disable a startup program. Some applications force their updaters to run from a Windows service instead of a normal startup entry. Go to Settings, Apps, Installed apps, find that program, and change its update settings inside the application itself rather than disabling it in Task Manager.
- Your hard drive shows high usage even when idle. This may be Windows Search indexing or the defragmenter running its scheduled task. Open Task Manager, identify the process, and wait a few minutes. If it never settles, check Windows Update for pending downloads that may be running in the background.
- You removed a startup program but it came back. Reinstall the application and disable its startup entry after installation. Many programs re-register their startup entries every time they update. If the problem persists, use the program's own settings to disable "launch on startup" rather than overriding it from Task Manager.
- The machine freezes completely. Do not force a shutdown immediately. Wait three to five minutes, because a major Windows update or a large file copy can occasionally pause the system. If nothing recovers, hold the power button for ten seconds, restart, and run Check Disk by typing cmd in search, right-clicking Command Prompt, selecting Run as administrator, then typing chkdsk /f and pressing Enter.
Advanced Tips for Fixing a Slow Computer
- Upgrade the RAM. If you regularly use more than 80% of your installed memory, adding RAM delivers immediate improvements. Check how much memory you have in Task Manager under the Performance tab, then verify whether your machine uses laptop SODIMM or desktop DIMM modules before ordering more.
- Replace a mechanical hard drive with a SATA SSD. This is the single most effective upgrade for an older desktop or laptop. A 500 GB SATA SSD costs around £40–£50, and you can clone your existing drive with free software and a USB adapter.
- Clear browser extensions. Ten or fifteen browser add-ons each consume 100–200 MB of memory, and they run on every page you visit. Open your browser's extension manager, disable everything you have not used in two weeks, and restart the browser. This can dramatically improve web performance even when the rest of the system feels healthy.
- Use a lightweight antivirus. Some paid antivirus suites use several gigabytes of memory and run constant scans in the background. Remove third-party antivirus, let Microsoft Defender stay active, and rely on safe browsing habits instead of heavy security bundles.
- Check for malware that consumes resources. If you cannot bring CPU usage below 50% at idle, run Windows Security's full scan, then install the Windows Malicious Software Removal Tool update directly from Microsoft. These two scans catch most common malware without additional software.
How To Fix A Slow Computer FAQ
- How often should I restart my computer? Once a weekend is a good baseline for heavy daily users. If you only use your computer during work hours, a single restart on Monday morning clears the weekend's background tasks and quickly renews memory. Frequent restarts cause no harm to modern hardware, so there is no downside to doing it daily if you prefer.
- Will deleting temporary files delete my passwords or saved logins? No. Temporary files are separate from saved credentials, cookies, and browser profiles. Removing them clears cached images and partially downloaded updates, but your browser logins and saved passwords stay intact. If you are especially cautious, skip the "Downloads" folder option when running Storage Sense or Disk Cleanup.
- Is it safe to use a Registry cleaner? No. Microsoft does not support registry cleaners, and they can corrupt system entries that Windows manages on its own. Manual registry editing never appears as a recommendation in this guide, because the risks outweigh the benefits. Windows Update and Reset this PC handle any registry problems more safely than third-party tools.
- Why is my computer slow when it has enough RAM and a fast SSD? A fast heart does not help if the arteries are blocked. Your browser extensions, startup programs, and background updaters may still consume every spare cycle. Review the Task Manager steps above, look for any process using over 30% CPU, and disable anything you do not need. Also check for thermal throttling, where a laptop with blocked vents slows down to prevent overheating; clean the vents and use a cooling pad if the underside feels hot.
- How much free space should I keep on my main drive? Keep at least 15% of total capacity free on a traditional hard drive and 10% on an SSD. SSDs slow down dramatically when they are over 90% full because the controller has fewer empty blocks to write to. If you are above this threshold, move media files and documents to an external drive, and archive files, you do not access monthly.
- Can I use these steps on a Mac? No. This guide is written for Windows 10 and Windows 11 only. Macs use different tools, a different file system, and different terminology. For a Mac, close unused apps, clear browser cache, check Activity Monitor for hungry processes, and verify that your startup disk has at least 15% free space.
- What is the fastest fix for everyday slowdowns? The restart. Restarting clears the most common short-term issues in under five minutes, and it costs nothing. If the machine runs well for a day and then slows again, work through the startup program and storage steps next, because those fix recurring slowdowns at the source.
Next Steps After Your Fix
- Test your computer for a full day before deciding whether you need more fixes.
- Write down your current storage usage and free space number so you can track improvements over time.
- Schedule a reminder to restart your computer every Sunday evening to stay preventive.
- Make a list of any programs you disabled during this guide so you know what to re-enable if you miss them.
- If the machine is still slow after this complete process, call a local repair service for a hardware check, particularly the drive and RAM.
FAQ
Common Issues
If the result is not working as expected, return to the previous step, check the material or setting involved, and make one adjustment at a time for how to fix a slow computer.
What should I check before using this advice?
Check the current details that apply to how to fix a slow computer, including availability, local rules, timing, compatibility, and any personal constraints.
Who is this guidance best for?
It is written for readers who want a practical starting point and are prepared to compare the advice with their own situation before acting.
What is the simplest next step?
Start with the first low-risk action, check the result, and make one adjustment at a time rather than changing several things at once.
