Nice, quick article from TechRepublic suggesting: "10 things you can do when Windows XP won’t booot".
- Use a Windows startup disk
- Use Last Known Good Configuration
- Use System Restore
- Use Recovery Console
- Fix a corrupt Boot.ini
- Fix a corrupt partition boot sector
- Fix a corrupt master boot record
- Disable automatic restart
- Restore from a backup
- Perform an in-place upgrade