GG,
there are a lot of great sugestions here and I'a like to offer one or two more.
If you want a nice, easy to use registry cleaner, among other things, check out www.Toniarts.com
he's got a good one there with specific win XP patches. It's free and easy to use.
CHECK your drivers!!!
I had some XP issues with older drivers, updated them and everything was hunky dory.
Use the windows update feature to make sure everything is up to date!
XP does haev it's share of flaws, but you can make it dance to your tune with patience and a bit of work.