when I put a cd into my computer to play it, nothing happens. How do I get the computer to play my cds?

Play mp3 and dvd under Ubuntu install skype googleearth acroread and other stuffs using Medibuntu

First please install https://help.ubuntu.com/community/RestrictedFormats

You need to have extra repositories enabled..

Please first enable the universe and multiverse repository:

Open System → Administration → Software sources → [ Tab Ubuntu software ]

enable "Community-maintained Open Source software ( universe )"
enable "Proprietary drivers for devices ( restricted )"
enable "Software restrictecd by copyright or legal issue ( multiverse )"

Close and confirm the repository reload.

Then open a Terminal from the menu Applications→Accessories→Terminal

Tip: right click with mouse on the terminal title caption and select the item "Always on Top" doing this you will force the terminal window to stay on top of the other windows and you will find very easy to copy single row from this web page into the terminal...
Something more about using the terminal https://help.ubuntu.com/community/UsingTheTerminal

Then type or better copy and paste a row a time then press enter:
(Tip: select the single row to copy then right click into the terminal and to quick paste click with middle button of mouse )

and type or better copy and paste:

sudo aptitude install vlc smplayer mplayer

To get better dvd playback and optional packages here the medibuntu available software list http://packages.medibuntu.org/
you need to add the medibuntu http://www.medibuntu.org/ repository to your /etc/apt/sources.list file:
( here the medibuntu howto https://help.ubuntu.com/community/Medibuntu but see below )

In short please open a Terminal from the menu Applications → Accessories → Terminal and type or copy and paste:

sudo wget http://www.medibuntu.org/sources.list.d/`lsb_release -cs`.list --output-document=/etc/apt/sources.list.d/medibuntu.list; sudo apt-get -q update; sudo apt-get --yes -q --allow-unauthenticated install medibuntu-keyring; sudo apt-get -q update

-- give your user password when requested, you don't see nothing when you type it, then press enter

Now to install, type:

sudo apt-get update
sudo apt-get install ubuntu-restricted-extras libxine1-ffmpeg
sudo aptitude install libdvdread4 libdvdnav4 libdvdcss2 regionset gnome-mplayer
sudo aptitude install non-free-codecs w32codecs
sudo aptitude install gstreamer0.10-pitfdll gstreamer0.10-plugins-good
sudo aptitude install gstreamer0.10-plugins-ugly gstreamer0.10-plugins-ugly-multiverse

give your user password when requested, you don't see nothing when you type it, then press enter.

You can also install other Medibuntu repository provided optional software http://packages.medibuntu.org/ :

sudo apt-get install skype
sudo apt-get install googleearth
sudo apt-get install acroread

Hope this helps