If you don't care for Ubuntu 12.04 desktop, perhaps you should consider the
Kubuntu 12.04 Live DVD and install from it, if you like it? It should offer to
add to Grub beside your Ubuntu, etc. or allow you to replace Ubuntu on your hard
drive.

Or if you add Synaptic from the Ubuntu Software Center, if it's still called
that. Then in Synaptic you can add Metapackages, which are Kubuntu, Lubuntu, and
others. Then when you boot your computer there should be a way to select which
one you want to try.

I did this later with the Bodhi Linux, which is built for older computers, I
added Lubuntu as backup to its Enlightenment desktop and lots of my favorite
games, mouse cursors, screensavers, and backgrounds. I added so many KDE
applications that it also offers that desktop to me.