Try cleaning it.
If you dont want to do a clean install of the OS (guessing windows7) then try booting into fale safe mode and removing the virus.
Good programs to try with is Microsofts own "Microsoft Security Essentials", It´s free and i always use that for myself and suggest it to others since its easy to use, install and remove and doesnt take much power from the computers. http://windows.microsoft.com/sv-se/windows/security-ess...
The other thing you would want to run is Malwarebytes to search for Malware and spyware.
This is by far my favorite program to search for malwares. https://www.malwarebytes.org/