This may help, and it may not.
I had similar problems and I discussed it with others and I reached the conclusion that I could, perhaps, figure it out. Actually it turned out to be a con-figure!
I was thinking about removing SP2 altogether but felt that it was best to keep it for it's obvious announced value.
What I did first was to defrag my OS drive. The amount of stuff that was scattered was quite a sight but it sorted it. Startup was slower than normal, icons would not re-draw 'in a flash' as they had done and so it went on.
I then realised that maybe one further tweak would be to do a few boots. I did 8 in quick succession and things began to get better. Boot ups were quicker, re-draws on the desktop got better and after about a week it was just great - and here is the best bit - it was better and faster than before. My startup now on XP Pro is never more than 68 seconds and the whole machine runs like a good-un. It just needs time to settle, sort out your settings and figure out how you want your machine to run.
For what it's worth there is my result. Everything is fine.
