MAG 22" Widescreen LCD Monitor using as external monitor doesn't show DVD

Hey, I am trying to watch a a DVD on my laptop and external monitor, I can only see the movie on the laptop screen but external monitor is showing a black screen, I did install the drivers(I think) , what might be the problem??
Thanks all,

MC

One of the function keys (?F5) usually switches from laptop LCD display to external. Have a look in the laptop manual to be sureā€¦