Exactly! Your computer jam because its running Microsoft!
Believe it or not, Microsoft's security glitch is so big, even if
you do not visit funny websites or download virus, you will still
get spywares hidden deep inside your system.
I don't think scans will help. I tried an experienment with Norton
Internet Security 2006 last week. I make sure I have the latest
signatures and ran a scan on a virus file. Yes! I have this trojan
file for testing. And all it takes is 3 seconds for Norton to tell
me the file is safe. The file is a 100% keylogger set to send info
to my friend's com yet Norton told me its safe!
Best solution to your problem : Back up all data, and wipe your
hard disk. 