You could try to find a later kernel on one of the urpmi repositories...
e.g.
ftp://mirror.cs.wisc.edu/pub/mirror/...linux/official
The contrib and PLF repositories usually have later kernels available.
ftp://ftp.easynet.fr/plf/mandrake/
Note that even if you have urpmi set to pull from the remote repositories, it will not automatically upgrade your kernel.
You must explicitly specify it...
e.g.
urpmi kernel-2.6.8-12mdk kernel-source-2.6.8-12mdk
You need both the kernel and kernel-source, and often ATI and NVIDIA module drivers if you have one of these video cards....
urpmi kernel-2.6.8-12mdk kernel-source-2.6.8-12mdk NVIDIA-2.6.8-12mdk
Check the FTP repositories to see what kernels are posted there, usually these are the easiest to install.
You can then download the files locally and install from there or do both at once using the urpmi command above...
(If you have set your urpmi sources properly and have your networking set up as well... which may be difficult if you are lacking chiplevel support...)
The other recourse is to go right to 10.1 which does have nForce support in it.