Hopefully this is applicable to any motherboard using the nVidia nForce 4 (nForce4) chipset with an on board network adapter.
After trying various options including booting from a floppy and CDROM I finally started from scratch using the PXE network boot image. It takes a bit more configuration, but booting from the network is much easier to iterate on than burning CDROM after CDROM.
I configured a Ubuntu 6.06 RTS machine to supply dhcp and tftp services. See
DHCPD Quick Setup Instructions and
DHCP mini-HOWTO. I mostly used the man pages to configure tftpd.
Once I figured out the multiple BIOS settings to enable the onboard network card to PXE boot, it wasn't much trouble. In the BIOS under "Advanced" make sure "Onboard NV LAN" is enabled and "Onboard LAN Boot ROM" is enabled. After saving and rebooting, look under "Boot". In "Boot Device Priority" make the "1st Boot Device" NVIDIA Boot Agent". Now the PC should boot via dhcp/tftp.
I used the contents of /home/samba/unattended-4.6/bootdisk/tftpboot/ and the undis3c network driver to boot.
To use tftpboot:
Copy the contents of .../bootdisk/tftpboot/ to: /var/lib/tftpboot/
Copy the undis3c network image from /home/samba/unattended/unattended-4.6/bootdisk/images/undis3c.imz to: /var/lib/tftpboot/unattended/undis3c.imz
This should get you running Z:/dosbin/install.pl from the network share. From there you can follow the general instructions.