I think you have to reinstall xp, seems your os got so many problems.
if you can get a xp cd or recovery cd, there should be no problem. but the reinstallation my destory your grub loader and you may have to reinstall ubuntu if you still want to keep it in your comp.
if you cannot get a xp cd easily, ubuntu is quite a good choice. you can perform most tasks easily on it. however, it depends on your hardware competibility, my laptop got problem with sound, the earphone and speakers run at the same time...funny right
