How do you get rid of Downloader.Rameh.C when AVG doesn't even know it exists?

I spent 12 hours yesterday trying to get the 'Downloader.Trojan' off my computer. [Symantec's most recent update for this is June 2002!]

I looked in all the forums, did all the usual 'update your virus definitions' in Norton Antivirus, multiple scans in safe mode, downloaded four 'spyware' softwares, and none of it worked!