How to change your software repositories list in Ubuntu

1- create your software repositories list from the sources list generator site below

http://repogen.simplylinux.ch/index.php

then copy the list

2- take a backup of you old list

cd /etc/apt

sudo mv source.list source.list.old

3- paste what you have copied from step one in a new /etc/apt/source.list file

4- sudo apt-get update

;)