What slows down a computer and how to fix it

A slow computer usually comes from one of four things: too many programs running at once, a hard drive that is nearly full, malware or unwanted software, or a hard drive that is aging and failing. You can fix the first three yourself in an hour or two. The fourth requires replacing the drive, which a repair shop can do.

The fastest improvement comes from closing programs you are not using and removing software you installed but no longer need. The second-fastest comes from clearing out old files and temporary data. Both are free and take less than 30 minutes.

Key Takeaways

  • Closing unused programs and removing software you no longer need often speeds up a computer noticeably within minutes.
  • Deleting old files, downloads, and temporary data can free up 10 to 50 gigabytes of space and improve performance.
  • Running a malware scan with Windows Defender (built into Windows) or a free tool like Malwarebytes can remove unwanted software slowing your system.
  • If your hard drive is nearly full or making clicking sounds, the drive itself may be failing and needs professional replacement.
  • Upgrading to a solid-state drive (SSD) is the single biggest speed improvement you can make, but costs $50 to $150 and requires installation.

Close programs running in the background

Every program you have open uses memory and processing power, even if you are not looking at it. On Windows, press Ctrl + Shift + Esc to open Task Manager. Look at the list under the "Processes" tab and find programs you recognize but are not using right now. Click on each one and select "End Task" at the bottom right.

Pay attention to programs that use a lot of CPU or memory—those numbers are in the columns to the right. Common culprits are web browsers with many tabs open, cloud storage programs like OneDrive or Google Drive, and antivirus software running scans. Closing a browser with 20 tabs open can free up 1 to 2 gigabytes of memory when ready.

Do not close anything labeled "Windows" or "System"—those are part of your operating system. If you are unsure what something is, search the name online before closing it.

Uninstall software you no longer use

Programs you installed months or years ago but never open still run background tasks and take up disk space. On Windows 10 or 11, go to Settings (press the Windows key and type "Settings"), then select "Apps" and "Apps & features." Scroll through the list and look for anything you do not recognize or no longer use.

Click on the program name and select "Uninstall." Windows will walk you through removing it. Do this for 5 to 10 unused programs and you may free up 5 to 20 gigabytes of space. Uninstalling also removes background processes those programs were running.

Be cautious with anything labeled "Driver" or "Chipset"—those are hardware-related and should stay. If you are unsure, leave it alone.

Delete old files and clear temporary data

Your Downloads folder, Desktop, and Documents folder often hold files you no longer need. Open File Explorer, navigate to each folder, and delete files older than a few months. Deleting old video files, installers, or project files can free up 10 to 50 gigabytes.

Windows also stores temporary files that pile up over time. Press the Windows key and type "Disk Cleanup." Open the tool, select your main drive (usually C:), and let it scan. Check the boxes next to "Temporary files," "Recycle Bin," and "Temporary internet files," then click "Delete Files." This usually frees up 1 to 5 gigabytes.

After deleting files, empty your Recycle Bin by right-clicking it on your desktop and selecting "Empty Recycle Bin." The files are not truly gone until you do this.

Scan for malware and unwanted software

Malware and unwanted programs can slow your computer significantly. Windows 10 and 11 come with Windows Defender built in. Press the Windows key, type "Windows Security," and open it. Select "Virus & threat protection" and click "Scan options." Choose "Full scan" and let it run—this takes 30 minutes to an hour but runs in the background.

If you want a second opinion, read Malwarebytes (the free version) from malwarebytes.com. Install it, open the program, and run a scan. Malwarebytes is particularly good at finding unwanted browser toolbars and adware that Windows Defender sometimes misses.

If either scan finds threats, let the program remove them. Restart your computer afterward. A computer infected with malware can be 50 percent slower than normal, so this step matters.

Check how full your hard drive is

A hard drive that is more than 85 percent full slows down noticeably. Open File Explorer, right-click on your C: drive, and select "Properties." Look at the pie chart—if the blue section (used space) takes up most of the circle, your drive is too full.

If you are above 85 percent full, delete large files you do not need (old videos, archived projects, backup files). You can also move files to an external hard drive or cloud storage like Google Drive or OneDrive to free up space on your computer.

If you cannot free up enough space and your drive stays above 85 percent full, you will need a larger hard drive. A 1-terabyte external drive costs $40 to $80 and plugs in via USB, or you can replace your internal drive with a larger one (which requires professional installation).

Consider upgrading to a solid-state drive

If you have done all the steps above and your computer is still slow, the hard drive itself may be old or failing. A solid-state drive (SSD) is 5 to 10 times faster than a traditional hard drive and is the single biggest speed improvement you can make. A 500-gigabyte SSD costs $40 to $70, and a 1-terabyte SSD costs $60 to $150.

Installing an SSD requires opening your computer case and connecting the drive, which is straightforward on a desktop but trickier on a laptop. Most people have a repair shop do this—expect to pay $50 to $150 for installation. After installation, your computer will boot in 10 to 20 seconds instead of 1 to 2 minutes, and programs will open noticeably faster.

If your hard drive is making clicking or grinding sounds, it is failing and needs replacement soon. Do not wait—back up your important files to an external drive or cloud storage first, then take the computer to a repair shop.

Frequently Asked Questions

Is it safe to delete files from my Downloads folder?

Yes. The Downloads folder is meant to be temporary storage. Once you have installed a program or opened a file, you can delete the downloaded file. If you need it again, you can read it once more. Deleting old downloads rarely causes problems.

What should I do if Task Manager shows a program using 90 percent of my CPU?

That program is the reason your computer is slow. If it is something you recognize and use, the program may have a bug or be stuck—close it and restart it. If it is something you do not use, uninstall it. If you do not recognize the name, search for it online before closing it, as some system programs have unfamiliar names.

Will disabling startup programs make my computer faster?

Yes, but only slightly. In Task Manager, go to the "Startup" tab and disable programs you do not need to run when your computer starts. This makes your computer boot faster but does not affect speed once it is running. Focus on the steps above first, as they have a bigger impact.

How often should I run a malware scan?

Run a full scan once a month, or when ready if you notice your computer is suddenly slow or you visited a suspicious website. Windows Defender runs quick scans automatically in the background, so you do not need to do those manually.

Can I speed up my computer without replacing the hard drive?

Yes—the first five steps above (closing programs, uninstalling software, deleting files, clearing temporary data, and scanning for malware) work on any computer and cost nothing. Most people see a noticeable improvement after doing these. Only replace the hard drive if the computer is still slow after you have done all of them.