If your computer has an optical drive with DVD playback capability, use Apple's DVD Player application. For information on optimal system settings for DVD playback, see technical document 42705 "
About Apple DVD Player, Version 2.7."
If you use Mac OS 9 and Multiple Users is enabled in the Multiple Users control panel, Apple DVD Player will open automatically when you start up your computer. To prevent this, open the Extensions Manager control panel and turn off the DVD AutoLauncher extension. To play a DVD video, open Apple DVD Player (in the Apple menu).