Have HijackThis fix this and see what happens:

O2 - BHO: (no name) - {AA58ED58-01DD-4d91-8333-CF10577473F7} - c:\program files\google\googletoolbar1.dll

Try scanning at:
http://symantec.com/avcenter/

Scroll down the page and click on "Check for Security Risks".

Seriously consider uninstalling the filesharing program(s). They are the root cause of many infections. You will continually get re-infected if you dont.

Install Spywareblaster and Spywareguard (links are below).

Tom