As John says, Antivirus, firewall, most antispyware, all useless in this situation. You might try a popupstopper (and popunderstopper) such as "EndTask" although I found this particular program little help and rather unrelliable but there are others. Try Tucows for free ones.

Article on "CoolWebSearch" in January PC Pro (UK) suggests CW shredder, although no longer being updated, as the best removal tool. www.spywareinfo.com/~merijn/downloads.html.

Also mentions BHOCop and CleanMyPC (but gives no link) for removing so-called "browser helper objects".

I repeat advice that once you have a clean install, put data and stuff on new partition, back up OS partition using Norton Ghost. That way you can usually get back to that clean install in about 20 minutes.