I'm assumming you mean S-Video out?
Heres what I do:
Connect my TV to my Powerbook via S-Video.
Go into Systsem Preferences, Click Detect Displays.
Go into arrangement, drag the menu bar from my main screen (powerbook) to the smaller TV screen.
Launch DVD Player, insert DVD and it plays on my TV.
This is video card dependant I assume, so your video card maybe lacking if this doesn't work.