I am trying to find a better driver for my graphics card and I tried using the 313 driver for Nvidia in the X.Org Stable ppa. After the process, i cannot boot into my ubuntu 12.04 partiton. i can boot with a live cd and access the partition and everything is there. How do I go back to the default drivers?
You must boot the corrupted Ubuntu system and login to a VT (CTRL+ALT+F2 ... F5) . Then remove the PPA you have added. Before that you should remove the nvidia driver first.
Now install ppa-purge and remove the ppa
I don't know this X.Org Stable ppa you said. If you meant X-Ubuntu Team then the above command should be
Reboot your system.
I suggest from now on to use only the Official Ubuntu packages (drivers especially)