PCI to AGP Video Problem

I have a Gigabyte GA6BXE Mainboard w/Pent. 500 and 128 M.B. Ram.I had an ATI All-In-Wonder pci video card in it. I am trying to install an Nvidia AGP card in it but it is as my M.B. will not allow AGP to work. I have set it to AGP in the Bios. Triedother AGP cards to no avail and tested the AGP cards I am trying.I see no jumpers on the M.B. for it.I have no idea what I could be doing wrong. Thanx in advance !