I suggest you download and run this software.
http://www.ewido.net/en/download/
You would be amazed how much evil stuff seems to get through virus checkers and install itself on your PC.
I have a Windows server that was compromised and neither Norton nor Microsofts Beta Anti Spyware product could find and fix the all the problems.
They scanned clean after removing many malprograms. This item found and cleaned 74 more files.
Only one more windows box to dump and we will be all Unix, Linux and Mac. I cannot wait.