Ubuntu Base:

To install KDE along with GNOME on Ubuntu (making it Kubuntu) you only need to run the command:

    sudo apt-get install kubuntu-desktop
    When it asks what dm to use; kdm or gdm; select kdm… continue…
    When done reboot (or restart x) and you have your Ubuntu ready for usage.
   
   
To install Xfce along with GNOME on Ubuntu (making it Xubuntu) you only need to run the command:

    sudo apt-get install xubuntu-desktop
    When it asks what dm to use; kdm or gdm; select gdm… continue…
    When done reboot (or restart x) and you have your Ubuntu ready for usage.
   
   


Kubuntu Base:

To add GNOME along with KDE on Kubuntu (making it Ubuntu) you only need to run the following command:

    sudo apt-get install ubuntu-desktop
    When it asks what dm to use; kdm or gdm; select gdm… continue…
    When done reboot (or restart x) and you have your Ubuntu ready for usage.
   
To install Xfce along with KDE on Kubuntu (making it Xubuntu) you only need to run the command:

    sudo apt-get install xubuntu-desktop
    When it asks what dm to use; kdm or gdm; select gdm… continue…
    When done reboot (or restart x) and you have your Ubuntu ready for usage.
   

   
   
Xubuntu Base:


To add GNOME along with Xfce on Xubuntu (making it Ubuntu) you only need to run the following command:

    sudo apt-get install ubuntu-desktop
    When it asks what dm to use; kdm or gdm; select gdm… continue…
    When done reboot (or restart x) and you have your Ubuntu ready for usage.
   
To install KDE along with Xfce on Xubuntu (making it Kubuntu) you only need to run the command:

    sudo apt-get install kubuntu-desktop
    When it asks what dm to use; kdm or gdm; select kdm… continue…
    When done reboot (or restart x) and you have your Ubuntu ready for usage.


If you want to switch from gdm to kdm or vice versa while having both do the following:

    sudo dpkg-reconfigure gdm
    and select your preferred dm
    or
    sudo dpkg-reconfigure kdm
    and select your preferred dm
   
If after installing a new desktop environment you wisht to switch the splash screen displayed during startup then run the following command:

$sudo update-alternatives --config usplash-artwork.so

Now you will get to answer a question regarding whether to use the Kubuntu, Ubuntu (or if you have it installed xubuntu) - desktop usplash imag. Select the one you want and rest at ease.



Getting Back to a Pure Base Install:

To get back to pure GNOME look at:
http://www.psychocats.net/ubuntu/puregnome

To get back to pure Xfce look at:
http://www.psychocats.net/ubuntu/purexfce

To get back to pure KDE look at:
http://www.psychocats.net/ubuntu/purekde