I really don't know if this is because your infected by some kind of thing.
But here is a tool , that show you rootkit , if you got one, i sujest you FORMAT right away. It possible to remove only if you already got the knowlege too.
http://www.gmer.net/index.php
Rootkit are very powerfull tool on a win32 computer, they hide thing from the windows API...
As example i told my rootKit to hide the word "Greenseed" you will no more see this text ABSOLUTE NOT ... Microsoft will soon gave a Service that cost much to be a member of they Anti RootKit Service... for me i think this should be free!
Rootkit are the most dangerous threat, since they can HIDE anything, PORT, PROCESS, HDD FREE SPACE, BANDWITH USAGE ...
Into another kind of idea! you maybe suffer from Interference , this is very possible and not rare thing with cheap Speaker system Amplifier.