please help - external monitor for macbook

hey,
i have plugged my macbook pro in to a plasma display and it clearly recognises the extra display, but when i go to load a dvd it only plays on the computer screeen. is there a way that i can get the dvd to play on the external display? i hear you can play with the lid of the laptop closed....is this possible? how do i go about it - if there is a tutorial or something that would be great (this is my first mac!!)
thanks

you need a mouse to play with the screen closed..

you could also set the other screen as the primary display by dragging the menu bar from your macbook screen to the plasma tv screen in the system prefferences under the display sub menu.