Hi, thyag,
My suggestion does not deal with "viruses", so to speak, but with Spyware.
These Trojans might possibly find their way into the same folder, but not sure.
One good free program is Spyware Blaster, available from:
http://www.javacoolsoftware.com/sbupdate.html
It has "definitions" available for downloading, about every 3 weeks or so.
It stops stuff from getting into the computer in the first place.
Another good one suggested by others is the Microsoft Anti-spyware program.
Best of luck.