Install all the patches for the game, the patches usually increase stability and compatibility, Because your on XP a fresh install should work without you having to tinker with it,
1. Install the patches,
2. I find its easier to run the launcher instead of starting the game itself, and set an affinity with the launcher then run the game through the launcher.
Set an affinity, Open task manager (ctrl+shift+esc) > Right click on the game launcher > select "go to process" > right click process > select "set affinity" > Select only one box, all other boxes should be unchecked > then press ok and play the game.
The above works like that for vista, it should be the same with XP but i havent used it in a while.