Originally posted by Hussein
Ripsnort to my knowledge SP1 didn't fix any major problem, instead it was MS's move to hose several illegal XP owners boxes.
No, that wasn't the reason for SP1. One of the big things SP1 does is provide ways to enable/disable or remove MS middleware as decreed by the Justice Dept. settlement. I estimate the majority of this service pack has to do with the justice settlement. They did tack on a little tightening of the illegal keys out there though.
SP1 worked great for me, and I've installed it on I think 4 machines now at home and work. It works fine, and I have not seen it cause any problems at all.