Trust me I know all to well the issue you are referring to .. I had 3 seperate machines all with Win98SE that all recieved MAXXs with plans to upgrade to Win2K. IIRC, the original box/literature says Win95, 98, 2000 however once 2K was installed on 2 of the PCs I found out the hard way it wasn't so. The short story of it being I emailed ATI, got a refund for 2 of the MAXXs (kept the 3rd running 98SE, still might have it somewhere) and did some more digging. You are partially correct, the issue was with how NT (2K) deals with PCI devices and AGP (going from memory here .. been some years). In Win9x ATI was able to use AFR however in 2K, the OS saw the AGP card as having 2 PCI devices, thus only 1 was able to work. I used to run a website (RadeonFAQ) and I believe there was a section covering it as well as the OLD Rage3D forums I had a write up under a different name (RageMAXX I think) that addressed it, gave support links to Intel's AGP spec as well as copies of the product boxes/manuals if any others needed to contact ATI for support/refunds. In the end the card was a great bridge product, it allowed ATI to remain competitive with the original Geforce 256 by using two Rage 128s until they could come out with the Radeon 256.
Edit: to make matters worse, VIA's implementation of Intel's AGP spec wasn't up to 100% and sadly they were the almost largest chipset supplier (just behind Intel) and trhe only real choice for AMD platofirms.
A bit OT:
BTW anyone still have the original Radeon 256 flash animation saved somewhere ?? Looked like a oval badge when completed.
*: "The apparent size and age of Fermi die suggests that many technologically advanced GPUs ought to exist.
However, this hypothesis seems inconsistent with the lack of observational evidence to support it."