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How to Check For and Remove Malware from Your PC

Last updated November 6, 2026 · By the PC Guide Info editorial team

Malware is software designed to harm your computer or steal your information. If your PC behaves strangely, work through these steps calmly.

Warning signs

  • The computer is suddenly much slower.
  • New toolbars, home pages or search engines appear in your browser.
  • Pop-ups appear even when no browser is open.
  • Programs you do not recognise are installed.
  • Your security software has been turned off.
  • Friends receive messages you did not send.

Step-by-step cleanup

  1. Disconnect from the internet if you suspect a serious infection, to stop data leaving your computer.
  2. Run a full scan. Open Windows Security, then Virus and threat protection, then Scan options, and choose Full scan.
  3. Use Microsoft Defender Offline scan if the problem persists. It restarts the computer and scans before Windows fully loads.
  4. Try a second opinion scanner from a reputable security company.
  5. Remove unknown programs in Settings, then Apps, then Installed apps.
  6. Reset browsers: remove unfamiliar extensions and reset settings to default.
  7. Update everything: Windows, browsers and other programs.

Change your passwords

Do this from a clean device. If the malware may have captured passwords, change them for email, banking and other important accounts, and turn on two-factor authentication.

When to reset Windows

If threats keep returning or you cannot be confident the system is clean, back up your personal files and reset the PC from Settings, then System, then Recovery. Be careful to scan your backed-up files before restoring them.

Prevent future infections

  • Download software only from official sources.
  • Do not open unexpected attachments.
  • Keep automatic updates on.
  • Use active security software and good backups.

Ask for help

If you have a work computer or sensitive data on the machine, contact your IT department or a trusted professional.

This article is for general information only and is not professional advice. Features, prices and menu names may change between software versions. See our disclaimer.