If you are just getting started in Ubuntu, I highly recommend that you check out my other guide "Ubuntu: Getting Started". It will help you get started in the basics of Ubuntu. That said, onto the instructable:
Ubuntu is a great OS, but one issue is that DVD decryption is not included by default because of legal reasons. DVD decryption allows you to watch DVD movies on your computer. In order to get DVD decryption, we need to install the restricted formats file. The restricted formats file allows you to read DVD's and do certain other things that you wouldn't be able to do by default.
This instructable is for ubuntu 10.04+, so if you are you a version of ubuntu earlier than 9.10, you will need to visit this website: https://help.ubuntu.com/community/RestrictedFormats/PlayingDVDs
Step 1: Open the Terminal
First, enter this command:
sudo apt-get install libdvdread4This command puts the necessary files on your computer to read the DVD's, now we need to enable them.
Now enter this command:
sudo /usr/share/doc/libdvdread4/install-css.shThis command installs and enables the previous command. We now have the files installed, but we aren't finished yet.
Step 2: Reboot
Rebooting will allow the changes we made to take effect. While your computer is rebooting, go grab a DVD to test.
Step 3: Test
I personally use "Movie Player". It came pre-installed on my version of Ubuntu and it works fine.
I have heard a lot about "Xine". If you don't already have it, you can download it by using the Ubuntu software center.