Not sure how far along you are, but here's the path I'd follow:
Check versions. There are at least three versions of AGP (and may be four, haven't been watching much lately). You may have a video card that only goes down to AGP2 and a mainboard that only does AGP1.
Next make sure the AGP is enabled. First I'd check BIOS, but some mainboards have a jumper to do this

. Then take out everything you can (PCI video cards, NICs, sound cards, speakers, monitors, mice, keyboards, vibrating chair

, etc. - everything but the AGP video card and that monitor, CPU, memory, mainboard and PS) and see if that works.
If you do not get a boot up screen (VGA text that says something like "UltraGeneric ROM 12/19/1973"

and lots of other information that flashes on the screen too quickly to read) then your OS is
not the problem, your hardware is fuxored somehow. It might still be some settings problem or incompatability problem, but it might not. If you reach this point, I'd suggest hitting technical forums, like
www.sharkyextreme.com and forums.anandtech.com.
Oh, and I'd try the latest bios instead of the earliest. And, poke around your mainboard's manufacter's website for any reports of problems and solutions. And, fire off an email to that company. It'll take a few days to get an answer, but they might have one.