Hi there - I own a computer store. I buy used Macs (mostly laptops), fix 'em, and resell them. IF the ones I buy are running Mac OS 9 (Maverick) or 10 (Yosemite) they 'may' have the previous owners Apple ID imbedded in the OS. While I TRY to get the previous owners Apple ID & Password, sometimes I forget to do that. To prep them for resale the 1st thing I do is create a NEW administrative account named "NEW OWNER" then reboot to that acct. and then "Secure Delete" the previous owners account. If the previous owner had bought software from the Apple Store and I attempt to do Apple Software Update the server "requires" an Apple ID Password. If I don't have that password it won't download an update to that app. If I do have the previous owners Apple ID password it will. But: Assuming that I do have the previous owners Apple ID and password: What do I do to REMOVE that identity from the computer before selling to a new owner who may have their own Apple ID and password? Thanks in advance for the advice... ?