If you have Ubuntu, and you can't play 99% of the videos and music, try this: Download the VLC player with the Package Manager (I assume you know how to do that) and install the player with all libraries which the Linux will ask you to install (everything is ~10MB). When the player is installed, you'll have a lot of new codecs, mp3, divx, xvid, rm (I didn't try this one), mpg and so on. You can play videos & music with the VLC player, but also with other players.
I saw that a lot of users on the forum use Ubuntu, and this might help someone...
Enjoy
