Remove the stupid Buddypicture.net link that shows up in AIM, from your computer. No matter what the website says, Buddypicture.net isn't "adaware", it *is* a virus. Allegedly, removal instructions on the buddypicture website doesn't work so I would advise against following their instructions.

Additionally, you can find the original instructions to remove the damn trojan here.

Oh, and don't forget to patch Internet Explorer (linked to October 2003 cumulative patch) to prevent this from happening again.