http://www.viruslist.com/en/viruses/...?virusid=73615
http://www.wilderssecurity.com/showthread.php?t=75245

See if you can download Kaspersky to eliminate the trojans. Or at the very least, it should point out the danger files and you can go into Safe Mode to delete them manually. The second link is pretty essential to your issue, as it seems to have occured several times. I suspect it may have happened through an unprotected Internet connection or suspicious email.

If you need clarification, I think I can help. I haven't dealt with this myself.