Re: Unable to install Nvidia driver
X is the graphics system. If you see pretty pictures and windows, you're probably using X.
It sounds like you're using xdm, kdm, or another display manager to "boot" to X. You'll need to start your computer in single-user mode to disable this. See your distribution's instructions for how to do this, since it differs (typically, you use the kernel image name (usually "linux") followed by "1" or "single" at the boot prompt.)
Single user mode is a good time to compile the nvidia driver, too.