also agree AVG free edition is very good and dosent leach as many recourses as the more well known virus apps. its all i use along with adaware and spybot.

another tip for stubborn malware, do a google search on the file name of the trojan, some have specific step by step fixes, also starting the PC in safe mode (repeatedly press F8 during the initial stages of start-up, and select safe mode from the list), then running the virus scan and removal is a good way to get rid of some nasties.