Avast and AVG are free, thats about their only positive. They won't hold a candle to say NOD32 in performance on scanning, catching, and preventing viruses.
I've been using avast for years and it's caught everything out there.
Try using VundoFix. This sounds oh-so-similar to Virtumonde/Vundo.http://vundofix.atribune.org/Please note, if this is Virtumonde and it has settled into your computer, the chances of getting rid of it without reformatting are very VERY low.