Hi Newbeejoe,
I am afraid you maybe out of luck. Your case is what they call SMALL Form Factor.
Here is your spec sheet:
http://support.dell.com/support/edoc...cs.htm#1110653
The only board that may fit in this case with a PCIe slot is the optiplex GX280, but I would contact Dell for compatibilty.
This board also takes DDR2 memory as most PCIe slot mobo use DDR2.
Bill