Too often machines become infected by something that slipped past even the best defenses. In these cases the choices are to either take the machine to someone that knows what they are doing or try and fix it yourself.
The free tools listed here are for brave souls who are trying to fix things on their own. We can not support or make any claim about these tools or web sites but have found them helpful for our own use on occasion. Have you thought about surfing with Limited Rights yet? Hope this helps.
SysInternals Security Utilities:
Ultimate Boot CD