After installing Ubuntu 11.10, you may find mp3 files and flash videos are not playing. Ubuntu provides an easy way to enable support for mp3, avi, flash playback support through its restricted extras package. Here is how to install ubuntu restricted extras package.
Update repositories and Install
Immediately after installing ubuntu, make sure that you have updated package list. To do this open Terminal (Ubuntu 11.10 Keyboard Shortcut: Ctrl + Alt + T) and copy-paste the following command
sudo apt-get update && sudo apt-get upgrade
Install restricted extras package
Ubuntu Software Centre or Synaptic package manager:
Search for ubuntu-restricted-extras and click install.
Copy paste the following code in the terminal to install the ubuntu restricted extras
sudo apt-get install ubuntu-restricted-extras