Since I last had to install the nvidia drivers in debian, things have changed a bit.
It used to be fiddly to get the nvidia drivers installed, but if you are running etch (or later) you should just be able to run (as root)
apt-get install module-assistant nvidia-kernel-common nvidia-glx
module-assistant auto-install nvidia
module-assistant install nvidia
Then just edit your X config (/etc/X11/xorg.conf) and change the driver line with “nv” to “nvidia” and restart your window manager and all should be running.
There is a wonderful howto with loads more detail at http://home.comcast.net/~andrex/Debian-nVidia/installation.html
