While it is a breeze to watch DVD in Windows and Mac OSX, it is definitely not a feature you would get when you install Ubuntu Gutsy. The default installation of Gutsy does not allow you to watch DVD due to legal and technical restrictions. You will have to install additional software to get the movie playing.
First, install the following library:
sudo apt-get install ubuntu-restricted-extras
This will install most of the codecs for multimedia (audio and video) playing.
Next, you have to install libdvdcss2 to watch encrypted DVD. The library package is not available in the Ubuntu repository, you have to use the libdvdread3 installer script.
This will retrieve and install the libdvdcss2. If it don’t work, download the deb installer at http://download.videolan.org/pub/libdvdcss/1.2.9/deb/libdvdcss2_1.2.9-1_i386.deb and click to install it.
Install the xine library
sudo apt-get install libxine1-ffmpeg
sudo apt-get install vlc
Now you should be to watch DVD in your VLC player.
If you want to use Totem Mplayer, you have to install totem-xine rather than using the default totem-gstreamer.
sudo apt-get install totem-xine