Wikipedia:Reference desk/Computing frequently receives questions about how to repair a Windows computer system that has symptoms of infection by a computer virus, Trojan horse, or other malware. Here is a list of recommendations.
First you should decide whether you want to try to repair the system in place and remove the virus or other malware; or whether you want to nuke the system from orbit and reinstall everything from scratch to guarantee a clean system.
- "Nuking your system from orbit" means you're going to make a backup of your hard disk, then reformat your hard disk, deleting everything. You will then install Windows, create new user accounts, and install all your applications. Finally you will selectively copy your data files from the backup to the hard disk. This procedure will eradicate any malware from your system files and applications; and should remove malware from your data files.
- "Repairing your system in place" means you will run anti-malware and antivirus software to attempt to identify and delete malware that has infected your system. This is more convenient, but it is not possible to be sure you have eradicated all of the malware, or that the system hasn't been damaged by the malware.