How to reset graphics driver to nv?

[Dennis Mattingly]

I made a small system change, and now X-Windows doesn't start, and I only
get a command line login.
Any help that I can get with getting my system to graphical mode again would
help.

Description:
Sometimes my Fedora detects correct resolution at bootup. Other times it
doesn't, and forces me to 800X600. Well, I got tired of 800X600 resolution
so I went to menu System -> Administrator -> Display. One of the options
there had me running nv driver, so I selected "NVIDIA manufacturer" option
and pressed okay. Now Fedora always dumps me to command line.

Any advice?
Thanks