We've got 2 pc's at work that have been taken over by some sort of ad trojan and keeps popping up unwanted adverts. It's very sneaky because it keeps replicating itself after we remove it's files and registry keys. I will not let it beat me - grr. I've tried cleaning it with AdAware and SpyBot and yet there it is, keeps on rearings it's ugly head.
Very clever though.