Windows sees optical drives as mainly a cdrom. You need a software program, like rclarke says, windvd or cyberlink power dvd. Also, the cd\dvd recording program called Nero has a dvd player with it as well.
You might want to look around on your start menu for such a program, you may have one already installed as they can be set to work when a dvd is placed in the dvd player, but they can also be set so that you have to go to the program you want to use and open it yourself to play the dvd.
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