Computers · Repair guide

How to fix a computer that's running slow

10 fixes, easiest first3 min readUpdated November 2026

Quick fix

Restart the PC, then open Task Manager with Ctrl + Shift + Esc, close what is using the most CPU, memory or disk, and disable apps you don't need on the Startup apps tab.

What it means

A slow computer is usually doing too much at once: too many apps or browser tabs open, too many programs starting with Windows, a nearly full drive, or a background task such as an update or scan. Less often it is malware, damaged system files or an older PC that is short of memory.

Common causes

  • Too many apps, browser tabs or startup programs running
  • A nearly full main drive
  • Windows Update or another task working in the background
  • Malware or unwanted programs
  • A power mode set to save energy
  • Damaged system files or a problem update
  • Not enough memory (RAM) or an older hard drive for today's apps

How to fix it

Work down the list. Each fix is safe to try before moving on to the next.

01Restart the PCEasy

  1. Save your work and close your apps.
  2. Select Start > Power > Restart.
  3. If the PC has been asleep for days or weeks, a restart alone often makes a big difference.

Why it helps: A restart clears memory and stops programs that have slowly piled up in the background.

02Find what is slowing it down in Task ManagerEasy

  1. Press Ctrl + Shift + Esc to open Task Manager.
  2. On the Processes tab, select the CPU, Memory or Disk heading to sort by the busiest apps.
  3. Close apps and browser tabs you are not using, or select one and choose End task. Do not end items you do not recognize under Windows processes.
  4. Open the Performance tab to see whether CPU, memory or disk is near 100%; that tells you which fix below matters most.

Why it helps: Seeing what is busy shows whether the slowdown comes from one app or from the PC running out of room.

03Stop unneeded apps starting with WindowsEasy

  1. In Task Manager, open the Startup apps tab. On Windows 10 it is called Startup.
  2. Right-click apps you do not need right away, such as game launchers or chat apps, and choose Disable.
  3. Keep your antivirus and anything you rely on enabled, then restart.

Why it helps: Fewer startup apps means a faster start and more free memory while you work.

04Free up disk spaceEasy

  1. Open Settings > System > Storage, select Temporary files, choose what to delete and select Remove files.
  2. In the same page, turn on Storage Sense to clean up temporary files automatically.
  3. Uninstall programs you no longer use from Settings > Apps > Installed apps, using More options (...) and Uninstall.
  4. Move large videos and photos to an external drive or cloud storage. Aim to keep 10-15% of the main drive free.

Why it helps: A nearly full drive slows Windows down and leaves no room for updates and temporary files.

05Install Windows and driver updatesEasy

  1. Open Settings > Windows Update and select Check for updates, then install what is offered and restart.
  2. Check Settings > Windows Update > Advanced options > Optional updates for driver updates.
  3. On Windows 10: use Settings > Update & Security > Windows Update.
  4. If the PC is slow right after updates install, give it some time; Windows may still be finishing work in the background.

Why it helps: Updates include performance fixes and newer drivers.

06Scan for malwareEasy

  1. Open Settings > Privacy & security > Windows Security > Virus & threat protection.
  2. Select Quick scan.
  3. If anything is found, follow the prompts to remove it, then use Scan options to run a Full scan.
  4. Uninstall any toolbar, browser add-on or program you do not remember installing.

Why it helps: Malware and unwanted programs use the CPU, disk and network in the background.

07Set power mode and visual effects for speedEasy

  1. Open Settings > System > Power & battery and set Power mode to Best performance. This uses more battery on laptops.
  2. Make sure laptops are plugged in when you need full speed.
  3. Select Search, type Adjust the appearance and performance of Windows, open it and choose Adjust for best performance on the Visual Effects tab.
  4. Select OK.

Why it helps: Power-saving modes slow the processor, and animations use resources older PCs can't spare.

08If it got slow after an update or new app, undo itMedium

  1. Back up important files first.
  2. New app: uninstall it from Settings > Apps > Installed apps.
  3. Windows update: go to Settings > Windows Update > Update history > Uninstall updates, select the newest update and choose Uninstall.
  4. On Windows 10: use Settings > Update & Security > Windows Update > View update history > Uninstall updates.
  5. Some updates cannot be removed; reinstall security updates once a fix is released.

Why it helps: A slowdown that starts right after a change is often caused by that change.

09Repair Windows system filesMedium

  1. Select Search, type cmd, right-click Command Prompt and choose Run as administrator.
  2. Type DISM.exe /Online /Cleanup-image /Restorehealth and press Enter. Wait until it finishes.
  3. Type sfc /scannow and press Enter. Leave the window open until it reaches 100%.
  4. Restart the PC.

Why it helps: Damaged Windows files can cause slowdowns, hangs and errors.

10Check whether the PC needs more memory or a faster driveAdvanced

  1. In Task Manager, open Performance and select Memory. If it is close to full during normal use, the PC needs fewer open apps or more RAM.
  2. Select the main disk. If it shows HDD and sits near 100% active time, an SSD upgrade would help most.
  3. Back up all files before any hardware upgrade.
  4. Ask your PC maker or a repair shop which memory or SSD fits your model; many laptops cannot be upgraded.

Why it helps: Older PCs with little memory or a spinning hard drive struggle with today's apps no matter how well they are tidied.

Check it's fixed

  • Apps open noticeably faster and the PC starts sooner.
  • Task Manager shows CPU, memory and disk well below 100% during normal use.
  • The PC stays fast after a few days of normal use.

When to get help

If the disk sits at 100% even with nothing open, or the PC is slow after all these fixes, have a repair shop check the drive and memory, since a failing drive can also cause slowness. Back up your files before any repair.

Questions

Why is my computer so slow all of a sudden?

A sudden slowdown often comes from an update or scan running in the background, a new app, or the drive filling up. Check Task Manager to see what is busy.

Why does my laptop get slow after a Windows update?

Windows often finishes setting up an update in the background for a while afterwards. If it stays slow for more than a day or two, check for newer updates or uninstall the latest one.

What does 100% disk usage mean?

The drive is fully busy and other tasks have to wait. It is common on PCs with older hard drives and is often caused by updates, scans or too many startup apps.

Do PC cleaner apps speed up a computer?

Windows already includes the tools you need, such as Storage Sense, Startup apps and Windows Security. Third-party cleaners are not needed and some cause more problems than they fix.

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