Miek

The one I use is proxomitron (http://www.proxomitron.org). Besides blocking pop-ups it can also remove ads from web-pages. Since it's working as a proxy-server you don't even notice any pop-up's that opens and closes immediately. This also means that it is working width any web-browser. It's completly free.

I've found this on the net about the change in Windows activation and Windows Update: Windows XP and Service Pack 1 (I don't know if it's true but it it might be) /Miek