Use Different Desktop Managers of ubuntu -- Part I

First of all, X Window Core must be installed, or you won't be able to use GUI. X Window Core is called "x-window-system-core". To install any GUI, you should install this first.

Display manager(Login manager): gdm/kdm/xdm, usually one of them is chosen. To get different desktop manager for ubuntu, just add packages following:
gnome: ubuntu-desktop
kde:      kubuntu-desktop
xfce:     xubuntu-desktop
With APT, you may type "sudo apt-get install ubuntu-desktop" in the console.

Install Part Finished
TO BE CONTINUED