I've been using Spybot for a while now, and combined with Ad-Aware it has cleaned out a very large number of dodgy items which had installed or hidden on my computer, including traces of stuff I thought I had got rid of months previously, but which had left loose files and registry entries behind.
Since my previous posting, I've been looking at some of the extra features it contains. If you install it - click on the section called "Tools", then select "Browser Pages" - this MAY help you to check or deal with your current problem, kat.
The section called "Hosts File" also allows you to block a massive list of problem websites/cookies sent from advertising popups.
Quack!
GtD.