If you surf the Internet while logged in as an administrator, you run a high risk of things being installed on your computer in the background. I can't answer your question directly, but when you do get the problem fixed, use one limited account to do everything except install programs. Switch to the password-protected administrator account only when required.

This way, even if something gets stuck on your computer, you can boot in safe mode with the administrator account and run a virus scan.

Also, when you are installing programs (such as AIM), spend a bit of time unchecking additional software youd don't need (such as WeatherBug).