If you want to solve this you have to start from the scratch, starting from 0 is always the best options and in this case is the only one that really deserves, but you can do that without losing any data simply copying the content of your partition into another one with the help of Ubuntu that you can run from a USB dongle in live mode.
I can't consider any other option simply because we really don't know what happens to your installation so every other move is really useless and can be too dangerous for your system and your data.
If you want to solve this you have to start from the scratch, starting from 0 is always the best options and in this case is the only one that really deserves, but you can do that without losing any data simply copying the content of your partition into another one with the help of Ubuntu that you can run from a USB dongle in live mode.
I can't consider any other option simply because we really don't know what happens to your installation so every other move is really useless and can be too dangerous for your system and your data.
My advise is to you that do fresh installation of Precise rather then upgrading it.Back up your all Home folder data before it.