I kept at this problem until I finally solved the issue, and I've since resorted perdormance to my FX 5200. By process of elimination I installed a kernel 2.4 branch that came with MDK 10.0 and tried the NVIDIA drives with that. No speed increase. I updated to Xfree86 4.4.0. No speed increase. I tried about 6-7 nvidia drivers to see if performance varied. It didn't. For anyone else who may have had this problem, here's what worked for me:
Firstly, the 4496 drivers seem to be the only ones capably of getting a good framerate out of my card. I don't know if that's a problem with the NVIDIA drivers, Mandrake, or with my card. Either way, the first step was to get the hacked NVIDIA 4496 drivers from minion.de.
Secondly, the minion.de 4496, while modified to work with 2.6 kernels, wasn't working proplerly from the get-go. glxgears output was around 2300fps (all other drivers ranked about 1700fps), but it couldn't display any textures correctly. glxgears would complain:
Xlib: extension "XFree86-DRI" missing on display ":0.0""
Issue: turns out the 4496 drivers were linking incorrectly to libGL.so.1. (At least, that's what I learned from the NVIDIA Linux forum.)
Answer: For me, it was as simple as removing the /usr/X11R6/lib/tls directory and run ldconfig. This sorted out any mislinked files.
(For more info ---> nV News Forum - XFree86-DRI missing with XFree86-4.3.0.-17 and up solved
This "unbroke" the NVIDIA drivers, so that 4496 drivers would show textures properly. For good measure, I then installed Mesa 5.0.2 (default for the distro) and ran "ldconfig" again (probably not neccessary.) Whether or not this had any bearing on the outcome, I don't know: it seemed to me that the card still wasn't running as fast as it should have been, but after installing mesa and running ldconfig again, something "clicked".
We'll assume, for simplicity sake, was the minion.de 4496 drivers and the problem with mislinking that caused so much frustration. The end result is that glxgears now clocks 3500fps as opposed to 1700fps before the fix. Max Payne (via WineX) struggled at 20fps and is now a smooth 60fps.