First, if you are using Ubuntu as your profile says, there's a much, much easier way to install nvidia drivers. Read this:
Now, if you are not using Ubuntu, you will really need to kill the xserver, completely. Fire up a virtual console (press CTRL + Alt + F3), login as root and type:
Go ahead and install the driver. When done, you will need to edit your /etc/X11/xorg.conf
. Find a line similar to this:
And substitute your "nv" (or whatever it is there) by "nvidia". Type "startx" or "telinit 5". That's it.