Hmm follow these steps and see if it helps:-
1. Select First Booting Device in BIOS as CD.
2. Boot from the XP CD, and select Repair option(press R for repair).
3. At the Recovery Console Prompt type bootcfg /scan , this will scan your computer for bootable drives and will provide you with the result.
4. Then type in bootcfg /rebuild to rebuild the boot loader configuration.
This should fix the booting problem.
If the above process doesn't help then type fixboot c: in Recovery Console Prompt where c: is the drive on which your OS is installed.