6.4.3. Problems with the X Window System (GUI)
If you are having trouble getting X (the X Window System) to start, you may not have installed it during your installation.
If you want X, you can either install the packages from the Red Hat Enterprise Linux CD-ROMs or perform an upgrade.
If you elect to upgrade, select the X Window System packages, and choose GNOME, KDE, or both, during the upgrade package selection process.