
That's very odd, I've never come across that one myself. You aren't using an old mobo, like a Skt7 because you need AGP 2.0 compliance (different from AGP2x and 4x which are multiplier speeds)? Updating with the latest non-beta drivers for ALL your hw may help, including BIOS and mobo drivers.

If you've tried multiple sources for drivers that rules out a faulty download or currupt driver file. Perhaps it is some Windows files which are corrupt or problematic although a re-installation of Windows is a bit of a pain and even a fresh install may not change it.

What card did you have in before, some people have found problems when switching between 3dfx, Radeons or nVidia cards, even older nVidia cards to newer nVidia cards can prove problematic. I would ensure all traces of previous gfx drivers are removed. If you can post a detailed system spec (inc manu, model and chipset) it may point to other factors.