Here are some ways of geting NVidia drivers working in Ubuntu 8.04 that have worked for me.
Using Ubuntu's Installer
sudo apt-get install nvidia-glx-new -y
sudo nvidia-xconfig
sudo reboot
Using EnvyNG
sudo apt-get install envyng-gtk -y
envyng -t
# type "1" to install NVidia drivers
# then "y" to restart
Using NVidia's Installer
#from http://www.nvidia.com/object/cuda_get.html -> Linux 32 bit
wget http://developer.download.nvidia.com/compute/cuda/2_0/linux/driver/NVIDIA-Linux-x86-177.67-pkg1.run
chmod +x ./NVIDIA-Linux-x86-177.67-pkg1.run
sudo /etc/init.d/gdm stop
sudo ./NVIDIA-Linux-x86-177.67-pkg1.run
rm ./NVIDIA-Linux-x86-177.67-pkg1.run
sudo /etc/init.d/gdm start
# this next step resolves a driver conflict.
# if we don't do this, the machine will start in low-graphics mode on reboot
sudo gedit /etc/default/linux-restricted-modules-common
# add 'nv' to DISABLED_MODULES ('DISABLED_MODULES="nv"')
sudo reboot
