Old home folder not recognized after upgrade, how to recover? Upon first boot after updating from 10.6.x to 10.8.x my friend started creating a new user account rather than importing the old one.

When I look in ~/Users/.. I see /new_account and /old_account, but when on the login screen I'm only seeing New Account and Guest.

Is there an easy way to get OS X to recognize the Old Account?  I was thinking there was something like blessing the folder, or maybe I need to add a user account with a matching name?
If you create a new account with the same name, it should prompt you to use the existing User folder.