Using xrandr

On my toshiba U305, xrandr -q shows three displays: VGA (the external VGA port) LVDS (the laptop's LCD screen) and TV (whatever TV is). To use the VGA display,the TV must be turned off, like so:

xrandr --output TV --off

Then you can toggle on the external display like so:

xrandr --output VGA --auto

This will make the external display the same as the laptop's LCD. To make it a separate 'area', try this:

xrandr --output VGA --auto --below LVDS

You may get an error that " screen cannot be larger than 1280x1280 (desired size 2304x800)". If so, modify /etc/X11/xorg.conf (make a backup first) by adding

Virtual 2304 800

to the "Display" subsection of the "Screen" section. See http://ubuntuforums.org/showthread.php?t=593906 for details.

05/26/2008