You can use a utility called Switchdesk,
which allows you to change to and from GNOME, KDE, and other
environments.
You can use Switchdesk from either the
shell prompt or from the login screen.
From a shell prompt, type
A window will appear (see Figure 13-1)
showing you the choices of environments you can select, under
Available Desktops. Once you select your new
environment, click on OK.
To see your changes take effect, you'll have to log out, then log back
in.
At the login screen, you can select environments by clicking on
and selecting an environment from the
pulldown menu that appears.
Now, just type in your username and password, and log in as usual.