Unity sucks as usual. Ubuntu Raring Ringtail 13.04 does not work properly on older machines (e.g. AMD core 2 with 2GB ram and on-board graphics) any more. It installs alright but xWindow crashes. Ubuntu-Gnome also had the same problem. In such situation Xbuntu (Ubuntu with Xfce) is a better option and we can add ‘Mate’ as Desktop environment to make it even better. Mate is the new name for the classic Gnome 2.0 Desktop. Until 10.04 Ubuntu was shipped with Gnome 2.0 Desktop.

To install Mate desktop in Ubuntu Raring Ringtail 13.04 open Terminal (Press Ctrl+Alt+T) and add one or all of following repositories:

sudo add-apt-repository "deb http://repo.mate-desktop.org/ubuntu raring main"
sudo add-apt-repository "deb http://mirror1.mate-desktop.org/ubuntu raring main"
sudo add-apt-repository "deb http://packages.mate-desktop.org/repo/ubuntu raring main"

Why three? Because one of these may be down at a given time as it happened in my case and I had to waste an hour to find other repositories. Now run the following commands from the terminal. One by one.

sudo apt-get update
sudo apt-get install mate-archive-keyring
sudo apt-get update
sudo apt-get install mate-core
sudo apt-get install mate-desktop-environment

This should do it. Now from next log in screen choose Mate.
In case of problem or for installing upon the other versions of Linux see official wiki page of Mate here.