With this file it is possible to use following commands:
$startx --layout Both (TwinView, CRT on the left side)
$startx --layout Clone (CloneMode)
$startx --CRT (Use only the external monitor)
$startx or: $startx --layout LCD (Use only the internal LCD-display)
I hope it will help you to config your linux-installation.
Important: With this file it is not possible to use an external screen which is connected to the dockingstation (Dell).