If your system fails to run due to an error corresponding to missing HAL.DLL, invalid Boot.ini or any other critical system boot files you can fix this by using the XP installation CD. Simply boot from your XP Setup CD and enter the Recovery Console. Then launch "attrib -H -R -S" on the C:\Boot.ini file and delete it. Launch "Bootcfg /Rebuild" and then Fixboot
Just wanted to share my new experience.
If your system fails to run due to an error corresponding to missing HAL.DLL, invalid Boot.ini or any other critical system boot files you can fix this by using the XP installation CD. Simply boot from your XP Setup CD and enter the Recovery Console. Then launch "attrib -H -R -S" on the C:\Boot.ini file and delete it. Launch "Bootcfg /Rebuild" and then Fixboot
Regards,
Carl