It's a pain that ubuntu does not play DVDs 'out of the box' as it were.

To fix this, quite simply, open a terminal session and type:

• sudo apt-get install totem-xine libxine1-ffmpeg libdvdread3
• sudo /usr/share/doc/libdvdread3/install-css.sh

That should be it!

Note that the DVD decrypting tool you're installing is not licensed or supported by ubuntu, so tread carefully. I have never experienced any issues with the above commands however.