dual screen

[Rakotomandimby Mihamina]

Hi all
Using xfce 4.6 (xUbuntu 9.04) on a laptop with ATI card.
the laptop has a VGA slot.

When I plug a screen on the VGA slot, then press Fn+F5 (it's
the laptop's key combination to activate the plugged screen)
I have the external screen turned on (the main screen stays on).

The default behaviour is to clone the main screen.
It's usefull for me when I make a demo, perfect.

Then, when I want to work with the 2 screens, I cannot:
I found no way to use "extended desktop on them"
(I want not clone but use a big desktop with the two screen)

When I enter Settings -> Display (while the external screen plugged)
it lists only one screen.

How at least to make XFCE detect the second screen?
I "think" once XFCE detects that second screen in its listing he will
be able to extend the desktop on them...

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