So, I should boot from the CD and select to repair the installation? Is
this why it keeps rebooting? I thought I tried the suggestions Russel gave
and changed the CPU Host Clock Control to 133. But it still reboots.
Perhaps I should boot from the cd and attempt the repair? Old MOBO was an
Asus P4S533.

You have changed from SIS-Chipset to intel-Chipset. They are not
compatible. Therefore you must do a repair installation of XP and then
you have to install the intel Chipset driver from CD, delivered with
the mobo. Otherwise your PC will not run.

Udo Kammer