It's not difficult to hide a virus in a file sharing site. Most P2P networks will let u report anyone who disguises viruses as files (some file sites even insist that all files must be labelled correctly to use their service). However, telling the network about a dodgy user isn't going to take that virus off your machine. So...
Be sure to visit your anti-virus supplier every week for a virus definition update- out of date virus definitions you leave your machine open to infection.
Check u haven't got Spyware on your machine. There are two Spy zapping tools that come out on top...
Spybot | Adaware
