Why is my computer so slow all of a sudden? 10 fixes for Windows 11

Your computer was fine last week. Now it takes forever to boot, apps freeze, and the fan sounds like a jet engine.

By the end of this guide you'll know what's dragging it down and how to fix it, or whether the hardware is on its way out.

The short answer

Restart the computer (a real restart, not shutting the lid). Then open Task Manager and see what's eating your CPU, memory, or disk. Nine times out of ten it's a stuck update, a runaway app, or a drive that's almost full.

Before you start

• Time: 15–30 minutes for the first fixes, longer if you run a full virus scan.
• What you need: your Windows password and a charger if it's a laptop.
• Back up first if the computer is freezing, clicking, or showing disk errors. A slow drive can be a dying drive. Copy your important files to an external drive now. If you're relying on OneDrive alone, read why sync isn't a backup.

1. Restart it properly

1. Click Start → Power → Restart.

Choose Restart, not Shut down. Windows uses a feature called Fast Startup that saves part of the system when you shut down, so problems can carry over. Restart clears everything.

If it's quicker afterward, something was stuck in memory. Keep going anyway to find out what it was.

2. Find the culprit in Task Manager

1. Press Ctrl + Shift + Esc to open Task Manager.
2. Click Processes in the left sidebar.
3. Click the CPU column header to sort by usage. Do the same for Memory and Disk.
4. Look for anything stuck near the top with a high number for more than a minute.
5. If it's an app you recognize and don't need right now, right-click it and choose End task.

Don't end anything labeled as a Windows or system process. If you see a name you don't recognize using a lot of resources, search the exact name before touching it.

Disk at 100% for minutes at a time is a big clue. That usually points to updates, a full drive, or a failing drive. All three are covered below.

3. Cut down your startup apps

Every app that launches at boot slows down startup and keeps eating memory in the background.

1. In Task Manager, click Startup apps in the left sidebar. You can also go to Settings → Apps → Startup.
2. Look at the Startup impact column.
3. Right-click anything marked High that you don't need the moment you log in, and choose Disable.

Disabling doesn't uninstall anything. The app still opens when you click it. Leave your antivirus and any audio or touchpad drivers alone.

4. Finish pending updates

Half-installed updates are one of the most common causes of a sudden slowdown.

1. Go to Settings → Windows Update.
2. Click Check for updates and install everything listed.
3. Restart when it asks, even if it asks twice.

You should see "You're up to date" when you're done. Expect a slow day or two after a major update while Windows reindexes your files in the background.

5. Free up disk space

Windows needs breathing room. When the main drive gets close to full, everything slows down.

1. Go to Settings → System → Storage.
2. Check how full your C: drive is. Aim to keep at least 15–20% free.
3. Click Temporary files, check the boxes, and click Remove files. Be careful with Downloads, since it deletes everything in that folder.
4. Turn on Storage Sense so Windows cleans temp files automatically.
5. Go to Settings → Apps → Installed apps, sort by size, and uninstall programs you don't use.

6. Run a full malware scan

Malware often runs quietly in the background, mining crypto or sending spam, and slows everything down.

1. Open Windows Security from the Start menu.
2. Click Virus & threat protection → Scan options.
3. Choose Full scan and click Scan now. This can take an hour or more.
4. If it finds something, follow the prompts, then run Microsoft Defender Offline scan from the same menu. It restarts the PC and scans before Windows loads, which catches threats that hide while Windows is running.

If a pop-up told you your computer is infected and gave you a number to call, that's a scam. Read how fake virus pop-ups work before calling anyone.

7. Tame your browser

Browsers are often the real reason a computer feels slow.

1. Close tabs you aren't using. Each one uses memory.
2. In Chrome or Edge, open the menu and go to Extensions. Remove anything you don't recognize or use.
3. Press Shift + Esc in Chrome or Edge to open the browser's own task manager and see which tab is the heavy one.

8. Check your power mode

Laptops often save battery by throttling performance.

1. Go to Settings → System → Power & battery.
2. Set Power mode to Balanced or Best performance while plugged in.

Still not working? Try these

9. Check for overheating. A hot computer slows itself down on purpose to protect the chip. Get the laptop off the bed or couch, clear dust from the vents, and keep it away from radiators. When the steam heat kicks on in a lot of NYC apartments this time of year, a laptop on a desk near the radiator can throttle hard.

10. Repair Windows system files.

1. Right-click Start and choose Terminal (Admin).
2. Type sfc /scannow and press Enter.
3. When it finishes, type DISM /Online /Cleanup-Image /RestoreHealth and press Enter.
4. Restart.

These tools compare your system files against clean copies and replace anything corrupted.

Watch for signs of failing hardware. Stop and back up if you notice any of these:

• Clicking or grinding sounds from inside the computer
• Disk usage stuck at 100% even after the fixes above
• Files that won't open, or folders that take minutes to load
• Random freezes or blue screens
• Settings → System → Storage → Advanced storage settings → Disks & volumes → Properties shows a drive health warning (this appears on most newer SSDs)

Older computers with spinning hard drives also get slower with every update. Swapping in an SSD often makes them feel new. If you're weighing that against a new machine, see our fix-or-replace cost guide.

Keep it from happening again

• Restart at least once a week. Don't just close the lid for months.
• Install updates when they come in instead of postponing them for weeks.
• Leave Storage Sense on and keep 15–20% of your drive free.
• Read the install screens carefully when you add new software. Uncheck any extra toolbars or "optimizers" bundled in.

Quick answers

Do I need a PC cleaner or "speed booster" app? No. Windows already has the tools you need, and many of those apps are junk or worse.

Will more RAM fix it? Only if Task Manager shows memory near 90–100% during normal use. If the disk is the bottleneck, more RAM won't help.

Should I reset Windows? Treat a reset as a last resort, and only after a full backup. It often fixes software slowness, but it won't fix failing hardware.

Want a tech to find what's slowing it down?

An ITGoNYC tech can connect through Remote Support ($79/hr). We'll find the process or startup app that's dragging things down, clear out malware, repair Windows, and check your drive's health while you watch. If the hardware is failing, we'll tell you straight and quote a Pickup & Bench repair ($149 flat) before any work starts. Call or text 347-549-9059 now for same-day help, or open a ticket.