DVD playback is protected from a number of angles. One is that most DVD software players will disable the second output for one simple reason. There is a fee imposed on each "stream" of video. To get the price low, they have to pay for one "stream" or the LCD in the case of a laptop.
You didn't tell if this was a DVD, so I can't know if this is your issue.
http://www.nwlink.com/~zachd/pss/pss.html also notes it may be possible to get WMP to display some video if you move the video acceleration down.
Best of luck,
Bob
Hi
I would like to watch the movies from my laptop on a TV. Mine is a compaq model, Evo N1020.I got a connecting cord and was able to see the display from my laptop on the TV. But my problem is when I play a video on my laptop and display on the TV is blank.
Could anyone help me solve this problem. Do i need to install special driver?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic