I know what it's like when you can't shake these things. Although I have my own online business I still work as a System Admin for a large company in the UK.
We have a trust policy with our PC users, we trust them not to download software or visit sites that are "potentially hazardous" but the inevitable happens and all too often I have spend my time sorting out the mess.
I use a variety of tools to remove unwanted programs including some very dodgy toolbars, sure I use spybot and adaware but my last resort is HijackThis.
If you are not an experienced IT user then I would stay away except as a last resort, this thing is viceous but very effective.
You can read about it and get a free copy at several sites including:-
http://www.spychecker.com/program/hijackthis.html
As I say, HijackThis is usually my last resort but I have to admit, it has got rid of the most stubborn programs.
Now if only I could find a program that would save me having to do the autopsy on the users PC to determine how it got there..... Ah well.
Regards
Steve
www.e-readit.co.uk
The Online bookstore
that offers you more.