What you could try depending on what the virus has done is to run sfc /scannow (assuming you use winXP and it may work for other MS systems). Heres a link
http://www.updatexp.com/scannow-sfc.html that will explain what it can do but you will need your xp disc if errors are found. On top of virus checkers and spy removal software its always a good thing to run if your having problems. You may find though, once its completed that you also have to download some updates from MS as it may step your files back to the cd versions that are known to be safe.
good luck with sorting your pc.