Make sure you download the latest security patches using Windows update. I had a
vicious case of t3h spyware/adware/virus combo until I got the latest "malicious software removal tool" from the windows update site.
It seemed odd to me that Windows Update was able to fix what Norton, Ad-aware, and Spybot couldn't, but it worked. I think I got the "Nail.exe" virus (well, actually someone that used my computer got it for me ...

), and I couldn't get it to budge until I downloaded the updates.
Anyway, give it a shot, and then re-run Norton, Ad-aware, and Spybot after that.