Here is a guide to install XBMC Media Center
XBMC is an award-winning free and open source (GPL) software media player and entertainment hub for digital media. XBMC is available for Linux, OSX, Windows, and the original Xbox. Created in 2003 by a group of like minded programmers, XBMC is a non-profit project run and developed by volunteers located around the world. More than 50 software developers have contributed to XBMC, and 100-plus translators have worked to expand its reach, making it available in more than 30 languages.
To install XBMC open a Terminal window (Applictaions -> Accessories -> Terminal) and copy+paste the following lines:
sudo add-apt-repository ppa:team-xbmc/ppa
sudo apt-get update
sudo apt-get install xbmc-standalone
When XBMC is installed you can find it under Applications -> Sound & Video