Ubuntu's commitment to only include completely free software by default means that proprietary media formats are not configured 'out of the box'.
Configuring these formats after a fresh install is simple. This guide will allowing you to play Flash, Java mp3, aac, DVDs ,mp4, avi, wmv and many more formats. It also installs the Microsoft true type fonts for better compatibility with Word documents.
In a terminal type:
sudo apt-get install ubuntu-restricted-extras