1 - open terminal
2 - install nano editor = sudo apt-get install nano
3 - edit sources.list = sudo nano /etc/apt/sources.list
4 - Add list lines=
deb http://old-releases.ubuntu.com/ubuntu/ oneiric main restricted
deb-src http://old-releases.ubuntu.com/ubuntu/ oneiric main restricted
deb http://old-releases.ubuntu.com/ubuntu/ oneiric-updates main restricted
deb-src http://old-releases.ubuntu.com/ubuntu/ oneiric-updates main restricted
deb http://old-releases.ubuntu.com/ubuntu/ oneiric universe multiverse
deb-src http://old-releases.ubuntu.com/ubuntu/ oneiric universe multiverse
deb http://old-releases.ubuntu.com/ubuntu oneiric-security main restricted
deb-src http://old-releases.ubuntu.com/ubuntu oneiric-security main restricted
5- save sources.list
6- sudo apt-get update