I have a laptop with SP1 installed, winver confirms this. If I try to install SP2 I get an error saying that SP1 must me installed, attempting to install SP1 produces a message that SP1 is already installed. This same SP2 patch downloaded, not using Windows Update, installed correctly on my desktop. When I tried using Windows Update it ran for abour 30 seconds and stopped, when I checked for available updates SP2 was still on the list.
Any suggestions?