This post might help some of you guys.
I installed the driver using the .run file in my brand new 9.1 installation, and everything worked fine. Then I built a custom kernel for my K6-III system, without bothering to deselect many modules I would not need (ie I built most things as modules).
Booted my kernel, and I could not have graphics, even though I reinstalled the driver.
After a lot of searching, it seems that there were two nvidia.o files in the lib/modules/...custom directory: one under ide/pci for the nforce chipset, and one in the kernel/video, which was the one I wanted. I renamed the ide module, and then everything worked.
Please note I am not at home now and cannot be absolutely certain for the subdirectories (eg was it ide/pci or pci/ide ?), but you get the general idea.
(btw, gears with the std kernel was about 390 fps, with the k6 kernel jumped over 500 fps --both with the 4363 driver. A weird performance increase, but I won't mind