The GeForce2 MX has an entirely different chipset that offers little-endian/big-endian compatability with Macs. There are also some other issues such as DVD playback involved. Older NVIDIA cards will not work with the Mac.
I have yet to see absolute confirmation that a retail GeForce2 MX will not work, but I would be very suprised if it did. NVIDIA does not manufacture cards, only chips. Creative, Asus, Guillemot and others make the cards and they are very focused on getting the most out of the PC market.