Have you tried this tool:

http://www.bitdefender.com/VIRUS-157247-en–Win32.Brontok.A@mm.html

Try a few rootkit scanners and see if they find anything:

http://www.f-secure.com/blacklight/

http://www.antirootkit.com/software/Panda-Anti-Rootkit-Tucan.htm

Could you post a HijackThis! log for us to look at?

http://www.bleepingcomputer.com/tutorials/tutorial42.html