After an automatic update, my computer would not boot, so I reinstalled Ubuntu from an optical disc (Ubuntu 12.10). This happened about a month ago; I had the most recent update. Installation instructions gave me the choice of getting the latest update online but said that if I got the latest update, I might lose my data, so I chose 12.10. However, my old data did not show up. How can I access it?
you simply reinstalled OS or did you format any partitions like ./ or /home? if so you you might have erased all the data you had if you didn't backed it up either. And it's also good if you used the same alias for username, if on previous OS you were Jimmy1 you should've stayed Jimmy1 not to become Jimmy13 or any other username info, because in this way you might have messed it up too.