Question : Need to Get Windows XP Pro booting - OS Must be missing a boot up file

I have a Windows XP Professional that after power down and then power up will not boot into Windows XP Pro.  Instead it just is in a constant BIOS boot loop.  I can get into the BIOS and I can also get to the F8 screen for OS Boot choices such as Safe Mode, Last known good boot etc.. I have tried all the choices but it never boots out of BIOS.

Last night the user was doing some clean up and may have by accident deleted a critical WIndows XP boot file.  Not sure.  

Does anyone know the easies way to get the system back booting normally?  

I can look at the hard drive with an external USB harness for the IDE hard drive and look at all files (copy files) to the hard drive if I could figure out what OS file may be missing.

I also have the WIndows XP Pro original CDs but I have not used "recovery" or other modes ever very successfully for this type of issue.  I do not want to have to do a fresh install of  OS or wipe out any user settings etc. if I can help it.

Any quick help would be greatly appreciated as I need to get this up and running ASAP.

Thanks in advance for your help.

Answer : Need to Get Windows XP Pro booting - OS Must be missing a boot up file

Press F8 during boot to get to the advanced boot options menu, then pick the option to disable reboot on error. Then, instead of the boot loop, you'll get the BSOD with the error message. What is the message?