Sony's PlayStation 2 was the first home game console to play DVDs, and if you have this classic system you can still use it for that purpose. Watching DVDs on the PS2 is simple, although if you don't have the dedicated DVD remote you'll have to remember the controller commands.
Watching DVD Movies
Switch on your PS2, plug in a controller and press the "Reset" button. The console's start screen will appear. Insert the DVD. Once the DVD begins to play, press "Select" on your controller to bring up the command menu. If you have the DVD remote accessory, you can use that to control the movie. Otherwise, you'll need to know the controller commands.
Controller Commands
Use the controller's D-pad to navigate around onscreen menu options. "X" functions as the "Enter" or "Play" key, while "Start" pauses and "Select" brings up the menu. Use "R1" and "L1" to skip between chapters and "R2" and "L2" to fast-forward and rewind. "O" stops playback.
Imported Discs
With the right preparation, your PS2 can play any kind of DVD, including imported discs or backups you've created. While the PS2 won't play these normally, programs such as Swap Magic or Region X allow you to bypass the console's restrictions. You'll need to perform a simple, non-invasive modification to let your console run with the disc cover open in order to make these work, but once you have you'll be able to play any DVDs you want.