It was so simple to solve. Just install ARandR controller and play with it.
It makes very easy the configuration of the 2 screens. External Screen and Laptop screen.
You can use the 2 at the same time, just the external and turn off the laptop screen, use the same desktop on the 2 screens or make and extension...etc.
All is on your hands.
After installing, go to "Preferences Menu" and then ARandR.
sudo apt-get install arandr
More info at : http://www.ubuntugeek.com/arandr-a-s...or-xrandr.html