First, delete or archive your current DVD player program.
Next, you just need to download pacifist from here: http://www.charlessoft.com/ to re-install the dvd player
Install it, then put your OS X install CD in your CD drive. Start up Pacifist (it will ask you if you want to buy it, just wait a few seconds and it goes away) Click the handy "Open Mac OS X install Packages" button. It will take a minue or two for the package list to load.. once it loads up, expand the "Contents of Essentials.pkg" thing. In that, expand the "Applications" folder. In that folder, you will see the file "DVD player.app" Drag that file to the applications folder on your computer, then try to launch it. If all goes well, it should launch.