if you have yum, then as root:
Code:
yum groupremove "GNOME Desktop Environment"
if KDE doesn't work after that then either try to update/re-install KDE
Code:
yum groupupdate "KDE (K Desktop Environment)"
yum groupinstall "KDE (K Desktop Environment)"
or decide it's not worth and just re-install Gnome.
Code:
yum groupinstall "GNOME Desktop Environment"
Either way, update us and tell us how it went.