Is it a legal version of Windows ? -- if so the Malicious software removal tool from microsoft removes it ! ( LINKIE )
Microsoft released the Microsoft Windows Malicious Software Removal Tool to help remove specific prevalent malicious software from computers that are running Windows 7, Windows Vista, Windows Server 2003, Windows Server 2008, or Windows XP. After you download the Microsoft Malicious Software Removal Tool, the tool runs one time to check your computer for infection by specific prevalent malicious software (including Blaster, Sasser, and Mydoom) and helps remove any infection it finds. Microsoft releases a new version of the tool every month.