Some index files failed to download. They have been ignored, or old ones used instead after apt-get update

Open a terminal (CTRL+ALT+T) and issue the following commands in order. SOLUTION: sudo cp /etc/apt/sources.list ~/ sudo wget "http://pastebin.com/raw.php?i=uzhrtg5M" -O /etc/apt/sources.list sudo apt-get update sudo rm /etc/apt/sources.list.d/ubuntu-extras.list sudo apt-get update This solution is not general. It is specific to the sources.list file of the Original Poster. The second command which starts with wget downloads and replaces the sources.list file with a specific for Precise (Ubuntu 12.04) sources.list file. See the file in raw format by visiting this page. The fourth command removes the ubuntu-extras.list file which had an impact/conflict with another file of the same, so we removed it to avoid the error