BFG Tech GeForce 6600 OC AGP

Someone suggested that I try posting this over here in hopes of a more
knowledgable response:

Well, I just got myself a shiny new BFG Tech card. I've tried both the
GeForce 6600 OC AGP and the GeForce 5500 OC AGP and both cards have had

the same problem. Basically my computer fails to render 90% of all
textures that rely on Direct X 9. I either got white shapes or blobs of

flattened texture on the surfaces that actually rendered /something/.
I've talked with tech support and they recommended that I download the
full install of Direct X 9 and try reinstalling it. I did, but the
problem persists.

And yes, I've run the Direct Draw and Direct 3D diagnostics. Those are
all clean, which is even more baffling. I just can't seem to play
things like Serene Screen's Marine Aquarium or the original Black and
White because I simply cannot see the textures. You try playing Black
and White without being able to see any trees sometime. :P

I'm running a Dell computer with a Optiplex GX240 motherboard with the
Intel 845 chipset and a Pentium 4 1.70 ghz processor. I have 512 MB of
RAM and I'm running Windows 98SE. I'm pretty sure I've got
all the latest updates as well, including for my chipset, my drivers --

with the exception of the Nividia driver, which I'm using the last
stable driver, 77.72 -- and all the security updates. I'm absolutely
stumped and I really don't want to have to try a reformat and install
again because I don't feel that will fix the problem and I really don't

want to take the card back because it's the only line I know that
supports Windows 98 still.

Have anyone else encountered this problem before? I'm at a total loss
and I think I've stumped tech support too. o.O