Often times when I have Windows XP installations which will not boot one of the first things I will try is a check disk from the recovery console. This will often times fix Windows file problems which are preventing Windows from booting properly. In order to do this you will need a Windows XP installation disc.
1. Insert your Windows CD and boot the computer.
2. Select the boot from CD option in your bios
3. Once you get to the set up screen instead of pressing enter to set up choose the second option which will tell you to press “r” for recovery.
4. Once the recovery console is booted it will ask you which Windows installation you would like to log onto. In most cases there will only be one but in the event there is more you will have to choose the one which was failing to boot.
5. Once the C:/ prompt comes up simply type “chkdsk /r” and sit bac and wait for it to complete. It may take a few hours depending on the size of the harddisk.
6. Once it is finished, remove the cd and reboot.