HOWTO: Install KDE on Ubuntu or Gnome on Kubuntu (and Xfce)

With an internet connection you can install:
kubuntu-desktop
67MB/108MB download, uses 312MB Additional HD Space

ubuntu-desktop
115MB download, uses 542MB Additional HD Space

So people who would want to do this might include:
-no internet connection available who had cd's mailed to them or burned by a friend
-who plan on installing either one more than a couple times before next release
-rolling it out on multiple desktops in a corporate environment
-or just wants to try out multiple desktops.

To install kubuntu-desktop KDE on existing Ubuntu

Insert Kubuntu CD
Ubuntu CD detected choose Cancel
Type: sudo apt-cdrom add
Ubuntu CD detected choose Cancel
Type: sudo apt-get install kubuntu-desktop
Logout | End Session
Session or Session Type choose KDE, then login.

To install ubuntu-desktop GNOME on existing Kubuntu

Insert Ubuntu CD
Ubuntu CD detected choose Cancel
Type: sudo apt-cdrom add
Ubuntu CD detected choose Cancel
Type: sudo apt-get install ubuntu-desktop
Logout | End Session
Session or Session Type choose GNOME, then login.

BTW: I know you can do it the graphical way from Ubuntu — insert Kubuntu CD, start package manager, search kubuntu-desktop, mark, apply, apply, choose kdm or gdm but I think the terminal way is quicker.

Xubuntu: How to install Xfce 4 Desktop Environment (like KDE/GNOME but super light weight) 14MB download but requires internet connection though.

Terminal Command:

sudo apt-get install xfce4 xfmedia xfce4-terminal xfce4-theme-brushedchrome

Alternately you may install these packages plus Xubuntu-Desktop via the Synaptic Package Manager or Adept.

Just search for "xfce" or "xubuntu" and install any packages that you wish.