XP usually fails if we remove Windows 2000 from a dual boot setup. You can remove it but it's painful to most.

Here's the drill:

1. Have your XP CD handy.
2. Use a partition program to delete the Windows 2000 partition and set your XP partition to the size your copy of XP can handle (this MATTERS!)
3. Now look up "XP REPAIR INSTALL" on google.com to fix most of the issues.
4. Now start reinstalling applications that have now failed.