MarvtheMan....Your P3 450 processor is a slot 1 ....I think. A good motherboard for you would be a
ASUS P3B-F slot 1 ..... it will handle up to a 800 processor, and fits a atx case ...
it has .....1 AGP slot
6 PCI slots
1 ISA slot
2 onboard USB ports
mouse and keyboard
serial and parallel ports
It will support up to 1 gb of 168 pin SD ram ( 4 slots) either PC100 or PC133 work in it just fine.
I picked one up on Ebay several months ago.
Check the Asus site in the archives for slot 1 boards and then go E baying.
Cheers,
dl65