Help! P3B-F Asus Motherboard and Radeon AGP card system freezing or rebooting itself

I have an Asus P3B-F Motherboard running a Pentium III 550 MHZ.
I am running Windows 2000 Professional.

I have not been able to use my Radeon AGP card
without the system freezing or rebooting itself several times a day.

I installed the Microsoft Windows Update and downloaded the latest drivers
from ATI

Please note that I also tested the system with a low end Diamond AGP card
and I having similar problems
Replacing the memory did not resolve the problem
Removing the network and sound card did not resolve the problem

Left with no alternative I am now using a PCI based Video card.

I have not had a single system crash or self reboot since
but I really would like to get my ATI Radeon card working.

Any help appreciated!
TIA
Dave