This will all need to be down from the Terminal Emulator which can be found from the “G-Menu” and clicking Accessories > Terminal Emulator.
First: Uninstall the previous XBMC’s on the device by doing the following:
sudo apt-add-repository -r ppa:wsnipex/xbmc-fernetmenta-master
sudo add-apt-repository -r ppa:team-xbmc/unstable
sudo add-apt-repository ppa:team-xbmc/ppa
sudo apt-get remove xbmc xbmc-bin
sudo apt-get update
sudo apt-get upgrade
Once you have done that you can reinstall XBMC:
sudo apt-get install xbmc xbmc-bin
You should now have the XBMC 12.3 installed on your box.