I´ve just intalled ubuntu and i cant play mp3´s, i get an error im totem player that say ¨failed to open reason unknown¨ musicplayer says ¨there is no plugin installed to handle a mp3 file¨

What do i do??

Make sure you have mpg321 or mpg123 installed. And did you install ubuntu to disk or is this their live cd?

Ubuntu is installed on my harddrive, i got it from from linux format the Feb eddition.
And where do i get ¨mpg321 or mpg123¨

Try this:
http://ubuntuguide.org/#codecs

Open the Synaptic Package Manager (Computer -> System Configuration -> Synaptic Packager Manager)

In the "Settings" menu click on "Repositories".
Enable (make a check in the box) the greyed out repositories. These are your "Universe" repositories. Click "Ok" to save these settings.

Click the "Reload" button to bring up the new list of packages. Now you have many options.

If you want Totem and rhythmbox (Music Player) to play mp3s, you need to install "gstreamer0.8-mad"
If you want a command line mp3 player, install "mpg321".
If you want something like Winamp to play mp3s, you should install "xmms" and "xmms-mad".

aptitude or apt-get install mozilla-plugins