If XP is corrupted to the point where none of the previous solutions get it to boot,
you can do a Repair Install that might work as well as keep the current settings.
1. Make sure you have your valid WindowsXP key
2. Insert and boot from your WindowsXP CD
3. At the second R=Repair option, press the R key
4. This will start the repair
5. Eventually you will be prompted for your XP key
