Can you confirm that this is occurring immediately at the completion of Setup and not at some later time after finishing Setup and performing other tasks on the machine?
Did you use the correct XP Setup CD for your machine, perhaps something that was supplied by Dell, or involved a Recovery Partition on the Dell machine?
If you try running Setup again you could remove from the machine all easily disconnected hardware such as USB, Printers, external drives, etc.,etc.
Have you tried running ChkDsk from Safe Mode.
Try running ChkDsk to check your drive for errors. Right-click your Drive icon/ Properties/ Tools/ Error Checking. Try it first by not checking either box (this will run it in a Read-only mode) to see if it flags any hard drive or file problems. If it does, restart it by ticking both boxes, and rerun it to allow it to attempt to fix any found problems.
The hard drive manufacturer will have free diagnostic software that is bootable, or that may even run from within Windows, that will thoroughly check the condition of your hard drive.
Check your RAM for problems.
156669 - How to troubleshoot a "STOP 0xC000021A" error
STOP 0xC000021a Caused by GoBack
XP Pro...Opens in safe mode only. Restarts in other modes
thread779-1310257
Have you tried setting your Bios to Safe Default settings? Perhaps there is a Bios update available.