I loved XP! Having started with MSDOS 2.x it was like the OS from the future. However it did have a few* problems.
1) XP did not seem to be able to free up memory after use. Photoshop was the worst culprit, it would grab all your memory and not release it when closing. (I know that memory use could be restricted in the Photoshop preferences).
2) Every bastard in the world wrote malware for it. XP became unusable. I ended up spending more time trying to keep it going than actually using it.
3)* other stuff :(
I abandoned Windows when Vista arrived, good luck to all of you who still need it.