Often times your computer might have a presentation mode, depending on manufacturer. I don’t do this all that often so I take the manual route…

This is how I display from an external monitor and turn my laptop monitor off usually (Vista):
– Right Click on Desktop
– Select Personalize
– Select Display Settings
– Select the Number 2 Screen
– Select the Extend the desktop onto this monitor
– Select the This is my main monitor
– Select the Number 1 Screen
– Unselect the Extend the desktop onto this monitor
– Select OK

This will display your desktop onto the external monitor and not your laptop (turn your laptop monitor off). To get back to normal reverse the steps for Screen 1 and 2. I haven’t really taken the time to figure out how to do this easier, but this way will work.

Like I previously mentioned Laptop Manufactures often have a Shortcut key to do this.

I have a Lenovo T61 and I can access their custom settings by selecting the Fn and F7 keys. A dialog box then comes up where I can choose from a few standard or customized scenarios.

On Dell PCs there is a Fn (Function) button push it the same time as F8 (or whatever button says CRT/LCD or has a picture of a monitor or two on it.

Look at ur f keys, whichever has a monitor on, usually f4 in the Uk, hold fn and tap until you have achieved the desired effect.