Question & answer

Can antivirus remove a virus that is already on my computer?

The short answer

Usually yes. A full scan with a good engine removes most common infections like adware, trojans and miners. For stubborn cases, add a second-opinion scanner like Malwarebytes Free. Then run a boot-time or offline scan such as Microsoft Defender Offline. Ransomware is the exception. Removing it does not bring encrypted files back, but a backup can.

In detail

Antivirus is better at prevention than cure, but cure usually works. On an infected machine, first update the security software. Then run a full scan rather than a quick one and let it quarantine everything it finds. Reboot and scan again. By then most everyday infections are gone, from adware and browser hijackers to trojans and cryptominers.

For anything left, work in layers. A second-opinion scanner can find what the first one missed. Every engine has blind spots. Malwarebytes Free is the usual choice and runs fine next to whatever you already use. Some malware hides while Windows is running. A scan before Windows fully loads catches it. Microsoft Defender Offline does this and sits in Windows Security under Scan options. A rescue USB from your antivirus vendor works too.

If the machine still misbehaves after all that, reset Windows. On modern Windows a clean reinstall takes about an evening and removes all doubt.

There are two limits to keep in mind. Removing ransomware stops the malware but cannot decrypt your files. Backups are the real defense there. If an infostealer ran on your machine, assume your passwords are compromised. Change the important ones from a clean device. Start with email and banking.