My computer has a virus or malware — what should I do?

Warning signs: sudden popup ads, a changed browser homepage, unusually high CPU/memory use, or software you don't remember installing. Disconnect from the internet, boot into Safe Mode, and run a full malware scan. Remove any unfamiliar browser extensions. For severe or repeated infections, a clean Windows reinstall (with your data backed up first) is often faster and more reliable than trying to chase down every trace of an infection.