I found a virus on one of PCs when avast was running a full scan. The win32:vndrop virus was detected and removed and was associated mousehook.dll. Once Windows fully loaded, virus was reloaded, changing the background saying I have a virus and an icon in lower right hand corner showing up also noting a virus with a link to website. I started with the standard 8 step procedure (http://www.techspot.com/vb/topic58138.html), but got stuck and could not load Malwarebytes' Anti-Malware. I am running on Windows XP home SP3.