xorg.conf is usually in the /etc/X11 directory as xorg.conf and it must be existing in one form or another for you to be using the gui.
I'm not familiar with fc6 though so it may be named something a little different.
X server is what gnome or kde runs on top of and is what uses the x config file.
If you do find it, make sure to make a backup of the original working file. so you can always go back and make it the current one again.
use a command like:
Code:
cp xorg.conf xorg.conf-original
or something of the sort.
-best wishes.