DVD Trouble


After installing OS X, I can't play DVDs when I'm booted in OS 9. I get an error message saying "Apple DVD player can't find software it needs." I tried reinstalling the DVD software and got the same error, what's wrong?
Also, I tried doing a clean install of OS 9, but when I restarted my Mac, it hung on the happy mac icon. I had to boot it up with the CD and use the older System Folder.