I gave my old MacBook Pro to my partner. Before doing so I deleted myself as the User, created her as User, deleted all of my docs & iPhoto Library. Unfortunately, the computer still thinks I am the User. For example, it tries to access MY iCloud content & asks for MY Apple ID. I've decided to replace the hard drive with a larger capacity one. I use Backblaze for backing up the laptop. If I do a clean install of Mountain Lion & then restore only docs & iPhoto Library from the backup, will that solve the double identity problem?
The erase (or the clean install of the OS) will ensure that only the new user is created. From that point, you can keep track of which files you restore in the unlikely case you feel things have become mixed again - but it's hard to see if you only restored a iPhoto library folder and files in documents how any user identity would be changed on the OS level.