You obviously don't have the kernel compiled with support for 64bit processors. If you know enough about your system, go grab the latest kernel sources from kernel.org and uncompress it to /usr/src.
NOTE: Become super user for the whole thing. Since you don't have X, use lynx and connect to ftp.kernel.org or transfer it from another comp or drive if you have a dual boot.
Use this command:
bzip2 -d /path-to-kernel-tarball.tar.bz2 /usr/src
ftp://ftp.kernel.org/pub/linux/kerne....4-rc2.tar.bz2
That's the link to the newest kernel. Now, time to compile it. Cd to the directory containing the kernel sources (cd /usr/src/linux-2.6.4-rc2) and type make menuconfig. If this is new to you then just navigate in it and choose what you need for your hardware. In processor type and features you'll need to make sure to choose the AMD 64 (K8) option.
After you have configured the new kernel, type "make bzImage && make modules && make modules_install && make install".
After everything gets done then within the /usr/src directory, type ln -s linux-2.6.4-rc2 linux to make sure the compiler and such knows what kernel it's working with and that the drivers get the kernel headers that are neccessary.
Now you'll need to configure your bootloader to run the new kernel. If you don't know how to do that, now is a good time to learn how. I use LILO, so here's my config section for the 2.6.4-rc2 kernel.
Code:
boot=/dev/hdb
map=/boot/map
install=/boot/boot.b
prompt
timeout=50
lba32
default=linux-2.6.4-rc2
image=/boot/vmlinuz-2.6.4-rc2
label=linux-2.6.1
read-only
root=/dev/hdb1
vga=0x317
append="root=/dev/hdb1 splash=verbose hdc=ide-scsi real_root=/dev/hdb1 init=/linuxrc"
image=/boot/vmlinuz-2.6.4-rc1
label=linux-2.6.4-rc1
read-only
root=/dev/hdb1
vga=0x317
append="root=/dev/hdb1 splash=verbose hdc=ide-scsi real_root=/dev/hdb1 init=/linuxrc"
image=/boot/kernel-2.4.20-gentoo-r6
label=linux-2.4.20
read-only
root=/dev/hdb1
vga=792
initrd=/boot/initrd-2.4.20-gentoo-r6
append="root=/dev/hdb1 init=/linuxrc"
image=/boot/vmlinuz-2.6.4-rc2
label=linuxnofb
read-only
root=/dev/hdb1
vga=normal
append="root=/dev/hdb1 init=/linuxrc"
image=/boot/vmlinuz-2.6.4-rc2
label=failsafe
read-only
root=/dev/hdb1
vga=normal
append="failsafe"
That is in /etc/lilo.conf and is only a model, so don't copy/paste mine without changing a bit.
If you use GRUB, then I'm not sure how to configure it but it shouldn't be much harder. After that, type lilo and if there are no errors reported then it should be okay to reboot. Also, make sure you point your bootloader to the actual old kernel because the new one will make a sym link to it that the old one might be set to and therefor you'll technically only have one kernel so if it doesn't work then you're screwed.
If you boot your system then run the installer for the nvidia drivers and it should work.
I also recommend possibly getting Gentoo because it makes doing this a breeze and can be customized for any application, desktop or server, and is very fast and lite.