The (deprecated) NFORCE driver package which NVIDIA had previously distributed via its website, is no longer supported. Please use the in-kernel modules with 2.6.17 (or later) kernels for the same hardware support that the NFORCE driver package provided.
Specifically, the forcedeth driver provides support for the onboard NIC(s), and audio is supported via the i810_audio, or snd-hda-intel (for MCP55 and later chipsets) drivers. Please see here for more information:
The driver package in the above URL includes pre-compiled RPMs and driver disks (which can be used for adding hardware support when installing the associated Linux distribution). Additionally, it provides the source for the forcedeth, sata_nv and amd74xx.c drivers. One thing to note is that the source is only included for distributions which do not already ship with the latest version of the corresponding driver.
To build forcedeth for your kernel kernel, create a new Makefile with the line:
obj-m := forcedeth.o
Then, type the command "make -C /usr/src/<kernel> SUBDIRS=$PWD modules" to build the forcedeth module for the kernel you specified.