Start with the fastest fixes first

A slow computer usually comes from one of three things: too many programs running at once, a hard drive that is nearly full, or malware. Before you reinstall Windows or buy new hardware, restart your machine, check how much disk space you have left, and look at what is actually consuming your processor and memory right now. Most of the time, one of these three steps will fix the problem in under an hour.

The order matters. Restart first because it clears temporary files and stops background processes that have been running since yesterday. Then check your disk space, because a drive that is more than 85 percent full will slow down even a new computer. Only after that should you look at what programs are actually running.

Key Takeaways

  • Restart your computer first, then check how much free disk space remains — a drive over 85 percent full will slow down any machine.
  • Open Task Manager on Windows or Activity Monitor on Mac to see which programs are using the most processor and memory right now.
  • Uninstall programs you do not use, delete large files you no longer need, and turn off startup programs that launch when you boot up.
  • Run a malware scan using Windows Defender (built into Windows) or a free tool like Malwarebytes to rule out infections.
  • If slowness happens only in one program, that program may have a memory leak — update it or reinstall it before assuming your whole system is broken.

Check your disk space and what is using it

On Windows, right-click your C: drive in File Explorer, select Properties, and look at the pie chart. If the blue section (used space) takes up more than 85 percent of the circle, your drive is too full. Windows needs free space to write temporary files and to move data around efficiently. When that space runs out, everything slows down.

To see what is taking up the most room, use the built-in Storage Sense tool. Go to Settings > System > Storage, and Windows will show you a breakdown by file type and folder. Look for old downloads, video files, and installer files you no longer need. Delete them. On Mac, go to Apple menu > About This Mac > Storage and click Manage to see the same information.

If you find that your Documents or Downloads folder is huge, open it and sort by date modified. Files from years ago are usually safe to delete. Video files, installer files, and old backup folders are common culprits. Move anything you want to keep to an external drive first.

See which programs are actually slowing you down

Open Task Manager on Windows by pressing Ctrl + Shift + Esc. Click the Processes tab and look at the CPU and Memory columns. The programs listed at the top are using the most resources right now. If you see something you do not recognize, search the name online — it might be a Windows system process that is supposed to be there, or it might be something you can safely close.

Common culprits include web browsers with too many tabs open (each tab uses memory), antivirus software running a scan in the background, and cloud sync programs like OneDrive or Google Drive. If your CPU is at 100 percent and nothing obvious is running, a malware scan is your next step. On Mac, open Activity Monitor (Applications > Utilities > Activity Monitor), click the CPU tab, and sort by % CPU to see the same thing.

If one program is always using a lot of memory, update it first. Outdated software often has memory leaks that newer versions have fixed. If updating does not help, uninstall and reinstall it. If the program is something you rarely use, uninstall it entirely.

Turn off programs that start when you boot up

Many programs add themselves to your startup list so they launch every time you turn on your computer. Each one uses memory and processor time, even if you never use it. On Windows, open Task Manager, click the Startup tab, and look at the list. Right-click any program you do not need running all the time and select Disable.

Be careful not to disable Windows system processes — if you are not sure what something is, search for it online before disabling it. Common programs to disable include Spotify, Discord, Slack, Adobe Creative Cloud, and cloud sync services if you do not need them running constantly. On Mac, go to System Settings > General > Login Items and remove programs from the list.

After you disable startup programs, restart your computer and notice whether it boots faster and feels more responsive. This single step often makes the biggest difference for users who have been installing software for years.

Run a malware scan to rule out infections

Malware and unwanted programs can slow your computer down significantly. Windows Defender comes built into Windows 10 and 11 and is free. Open Windows Security (search for it in the Start menu), click Virus & threat protection, and select Scan options. Choose Full scan and let it run — this takes 30 minutes to an hour, but you can use your computer while it scans.

If Windows Defender finds nothing but your computer is still slow, read Malwarebytes (the free version is enough). Install it, update it, and run a full scan. Malwarebytes catches some threats that Windows Defender misses. Restart your computer after the scan finishes.

If a scan finds malware, Malwarebytes will remove it automatically. After removal, restart your computer and check Task Manager again to see whether the slow programs are gone. In most cases, your computer will feel noticeably faster.

Delete temporary files and clear your browser cache

Windows stores temporary files in a folder that can grow very large over time. Open Settings > System > Storage, scroll down to Temporary files, and click it. Check the boxes next to Temporary files, Recycle Bin, and Downloads (if you want), then click Remove files. This usually frees up several gigabytes.

Your web browser also stores cached files and browsing history. In Chrome, press Ctrl + Shift + Delete to open the Clear browsing data window. Select All time, check Cookies and other site data and Cached images and files, and click Clear data. Do the same in Edge, Firefox, or Safari. This will not delete your saved passwords if you leave that box unchecked.

After clearing temporary files and cache, restart your computer. You may notice that websites load slightly slower the first time you visit them after clearing cache, because the browser has to read them again, but overall responsiveness should improve.

Update Windows and your drivers

Outdated Windows installations can run slowly because they lack performance improvements and security patches. Open Settings > Update & Security > Windows Update and click Check for updates. Install any updates available and restart your computer when prompted. This may take 20 to 30 minutes.

Outdated drivers — especially graphics drivers — can also cause slowness. Open Device Manager (search for it in the Start menu), right-click your graphics card under Display adapters, and select Update driver. Choose Search automatically for updated driver software. If Windows finds an update, install it and restart.

On Mac, go to System Settings > General > Software Update and install any updates available. Mac updates usually improve performance, especially if your machine is more than a year old.

Frequently Asked Questions

Why is my computer slow only when I open one specific program?

That program likely has a memory leak or is outdated. Update it first through its own settings or website. If updating does not help, uninstall it completely, restart your computer, and reinstall the latest version. If the problem persists, the program may not be compatible with your version of Windows or Mac.

How do I know if my hard drive is failing?

A failing drive usually makes clicking or beeping sounds, or shows error messages about corrupted files. If you suspect a failing drive, back up your files to an external drive when ready and take your computer to a repair shop. A failing drive will eventually stop working entirely, so do not wait.

Should I add more RAM to my computer?

Only if Task Manager shows your memory usage at 90 percent or higher while you are doing normal work. If your memory is not maxed out, adding RAM will not help. Check what you are actually running first — closing browser tabs and disabling startup programs is usually cheaper and faster than buying new hardware.

Is it safe to delete files from the Windows folder?

No. Never delete anything from the Windows, Program Files, or System32 folders unless you are following specific instructions from Microsoft or a repair technician. Deleting system files can break your operating system. Stick to deleting files from Downloads, Documents, Desktop, and the Temp folder.

How often should I restart my computer?

Restart at least once a week, or whenever you notice slowness. A restart clears memory, stops background processes that have been running too long, and applies Windows updates. Many slowness problems disappear after a straightforward restart.