Rootkits, a type of malware that hides itself, can be even trickier. For really nasty malware, your antivirus software may not be able to fully remove it from within Windows. Antivirus software will try to stop the malware and remove it, while the malware will attempt to defend itself and shut down the antivirus. If your computer is infected with malware, the antivirus software will have to do battle with the malware.

Standard antivirus software runs within Windows. RELATED: How to Remove Viruses and Malware on Your Windows PC The Problem With Cleaning Up Malware From Within Windows