Sony PCG-XG18 Primary User Manual page 75

Using a projector connected to your computer can be convenient for
presentations and slide shows.
When you connect an external display to the monitor connector, you can
toggle the output among the Liquid Crystal Display (LCD), the external
monitor, or both devices.
Use the Fn+F7 keys to select a display. See also "Selecting the Display
Mode" in the Customizing Your Notebook manual for more information.
Switch to an Fn+F7
external
display
Toggles among the LCD, the external display
connected to the Monitor connector, and both
the LCD and external display.