My Solution is that you update ur virus definitions and then runa through scan of your system and then refrain ur self from installing every shit that you find on the net !
PLEASE don't disable your Antivirus while you surf the net or checkout a CD from ur beloved friend ! Those are the places from where ur comp catches a Viral Infection
Always keep ur virus definitions up to date !
Since.........I faced the same probs some time ago (members of this forum told me the above) and it indeed turned out that the cause of my probs was negligency and the W32 viruses ! (W32.Pinfi in my case)