I've just had the problem over the weekend and have had success removing what turned out to be a large number of trojan viruses which found their way in through a fake email ecard I received.
I used the Dr Web Cure it programme which is free www.freedrweb.com/
I would recommend the 'Complete' scan. I ran the express scan first which allowed me delete about 7 viruses but when I ran the complete scan it found even more. The complete scan takes 2 hours.
Hope this helps