OS : Ubuntu Intrepid – Gnome.
In case you like to see a lot of movies you probably need to use from time to time the Screen Resolution utility from System->Preference in Ubuntu Intrepid to activate the second Tv screen. This utility seems to work in an unstable manner but from the reviews I read the next Ubuntu version (Jaunty Jackalope) took care off that. I like to wait a few months before upgrading to the new stable version so until then I found a great way to manage my LCD and VGA resolutions with ease.
To turn off your LCD display use
xrandr –output VGA –off
That’s it. It should work out off the box.