How to Check a Windows PC for Malware and Remove It

This guide walks you through checking a Windows PC for malware and removing anything you find. You’ll use built-in Windows tools first, then free third-party scanners for a second opinion, and finally manual cleanup steps if needed. No special skills are required—just follow the steps in order.

What You’ll Need

Administrator access to the PC (you’ll need to approve some actions).
A stable internet connection (to update definitions and download tools).
About 30–60 minutes of uninterrupted time.
An external USB drive or cloud storage to back up important files (optional but recommended).

Step-by-Step

Update Windows and your security software. Go to Settings > Update & Security > Windows Update and click Check for updates. Install all pending updates, then restart if prompted. This ensures you have the latest security patches.
Run a full scan with Microsoft Defender. Open Windows Security (search for it in the Start menu). Go to Virus & threat protection and click Scan options. Select Full scan and click Scan now. This can take an hour or more, so let it run. If it finds anything, follow the on-screen prompts to quarantine or remove it.
Run an offline scan. In the same Scan options screen, choose Microsoft Defender Offline scan and click Scan now. Your PC will restart and scan before Windows loads, catching malware that hides in the system. After it finishes, it will restart again.
Check for unwanted programs. Go to Settings > Apps > Apps & features. Scroll through the list and uninstall anything you don’t recognize or didn’t install yourself. Right-click and choose Uninstall. Pay special attention to recently added items.
Review browser extensions. Open each browser you use (Chrome, Edge, Firefox, etc.) and go to the extensions or add-ons page. Remove any extensions you don’t recognize or didn’t install. In Chrome: Menu > More tools > Extensions. In Edge: Menu > Extensions.
Run a second opinion scanner. Download and run a reputable free on-demand scanner like Malwarebytes (free version). Install it, update it, and run a Threat Scan. Quarantine anything it finds. This catches things Defender might miss.
Check startup programs. Press Ctrl+Shift+Esc to open Task Manager. Go to the Startup tab. Disable anything you don’t recognize or that seems suspicious (right-click > Disable). This prevents malware from auto-starting.
Clear temporary files. Open Disk Cleanup (search for it), select your system drive (usually C:), and click OK. Check all file types, especially Temporary files and Recycle Bin, then click OK and Delete Files. This removes junk that can hide malicious code.
Reset browser settings if needed. If your homepage or search engine changed without your permission, reset your browser. In Chrome: Settings > Reset and clean up > Restore settings to their original defaults. In Edge: Settings > Reset settings > Restore settings to their default values.
Restart and re-scan. After all steps, restart your PC and run another full scan with Defender to confirm nothing remains. If it comes back clean, you’re done.

Common Mistakes

Skipping the offline scan. Some malware can hide from a normal scan. The offline scan runs before Windows loads, so it can catch deep-rooted infections.
Using only one scanner. No single tool catches everything. A second opinion scanner like Malwarebytes is worth the extra time.
Ignoring browser extensions. Many “free toolbars” and “shopping assistants” are adware that track you. Remove them even if they seem harmless.
Not updating first. If your virus definitions are old, you’ll miss new malware. Always update before scanning.
Uninstalling system apps. Don’t remove anything that looks like a Windows component (e.g., “Microsoft Edge” or “Windows Security”). Only uninstall third-party programs you’re sure about.

Tips

Back up important files before you start. If you have to remove a stubborn infection, you might need to reset Windows, which can erase your files. Back up to an external drive or cloud.
Use a standard user account for daily tasks. Malware often needs admin rights to do serious damage. If you only use an admin account when necessary, you reduce the risk.
Keep everything updated. Regular Windows updates and browser updates close security holes that malware exploits.
Be cautious with email attachments and downloads. Most malware comes from phishing emails or fake downloads. If you didn’t expect it, don’t open it.
Consider a browser extension that blocks malicious sites. uBlock Origin or similar can prevent many infections before they start.

Troubleshooting

If the scan finds malware but can’t remove it: Try restarting in Safe Mode (hold Shift while clicking Restart, then choose Troubleshoot > Advanced options > Startup Settings > Restart, then press 4). Run the scan again in Safe Mode. Some malware can’t run there, so removal is easier.

If your PC is too slow to scan: Close unnecessary programs and run the scan overnight. If it’s extremely slow, try the offline scan first—it runs before Windows loads and may be faster.

If you see pop-ups or redirects even after cleaning: Reset your browser completely (clear cache, cookies, and restore settings). If that fails, check for unwanted browser policies in Settings > Apps and uninstall any suspicious programs. You may also need to check the hosts file (C:\Windows\System32\drivers\etc\hosts) for malicious entries—but only if you’re comfortable editing system files.

If nothing works and the infection persists: The safest option is to back up your personal files (documents, photos, etc.) and perform a clean install of Windows. You can use the Reset this PC feature (Settings > Update & Security > Recovery > Get started) and choose Remove everything. This wipes the drive and reinstalls Windows, which removes all malware.

Frequently Asked Questions

How do I know if my PC has malware?

Common signs include sudden slowdowns, frequent pop-ups, browser homepage changes, new toolbars, high disk or CPU usage with no open programs, and unexpected system crashes. If you notice these, run a scan.

Is Windows Defender enough to remove malware?

For most home users, yes. Microsoft Defender is a solid antivirus that catches a wide range of threats. However, adding a second on-demand scanner like Malwarebytes provides an extra layer of protection and can catch things Defender misses.

Can I remove malware for free?

Yes. Windows Defender is free, and Malwarebytes has a free version that works for on-demand scans. You don’t need to pay for removal tools in most cases.

Will I lose my files if I remove malware?

Normally no. Quarantining or removing malware doesn’t delete your personal files. However, if you need to do a full Windows reset, you may lose files if you don’t back them up first. Always back up before drastic steps.

How often should I scan for malware?

It’s a good habit to run a full scan monthly, and an offline scan every few months. If you visit risky sites or download lots of files, scan more often.

What should I do if I accidentally installed a fake antivirus?

Fake antivirus programs are malware themselves. Uninstall them through Settings > Apps, then run a full scan with Defender and Malwarebytes. Reset your browser settings as well, since they often change them.

General steps for current mainstream versions; menus can differ by device and version. See the disclaimer or report an error.

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