This may also be a driver related problem.
If your Windows XP CD is not an OEM one, you can try to repair the windows installation.
First, do a backup of all important files.
1. Boot into any live linux CD (as in post #2).
2. Locate all important files and copy to CD/flash drive.
Boot from the WIndows xp CD and proceed to the time you are given an option to repair, and then select repair.
If restore does not help, then do a clean install of xp (i.e. after formatting the system partition)
For OEM,
AFAIK, you must restore your system.
BTW, i'm not saying that repair/reinstall is the *only* solution to the problem, but it seems the *only* one given the information you have provided.