Note: This is a classic how-to intended for beginners and it describes how to install video codecs and DVD support on Debian Lenny in several easy-to-follow steps.
1. Add debian-multimedia.org repository to your sources.list file
To edit the /etc/apt/sources.list file, type as root:
Next, add the following two lines:
deb http://debian-multimedia.org/ lenny main
deb-src http://debian-multimedia.org lenny main
Save the file with ^O (CTRL+O) and close Nano with ^X.
For additional information about the debian-multimedia.org repository, visit the website.
2. Install debian-multimedia-keyring and update the list of packages
As root, type:
wget http://debian-multimedia.org/gpgkey.pub -O - | apt-key add - && apt-get install debian-multimedia-keyring
Then, to update the list of packages type:
3. Install w32codecs and libdvdcss2
apt-get install w32codecs libdvdcss2
That should do it. Next, you will need a video player, and I recommend one of VLC, SMPlayer or Kaffeine.
To install either of those, use:
apt-get install vlc
apt-get install smplayer
apt-get install kaffeine
That's it, you should be done now.