Take it from someone who learned the hard way and had to archive and install, completely rework all my plists, transfer tons of old files when I simply changed the home folder name. It is a huge kick in the... If you have already done it, as I suspect you have, and your computer is operating as if it were a brand new machine or is going all haywire, I suggest you 1. run disk utility as a basic safety measure and first step. 2. archive & install. I am giving you the quick and right to the punch steps, clearly there are other intermediate measures between 1-2 that can prove useful.