How do I recover the administrator or root password on OS X? I received a hand me down white MacBook with 10.4 on it and it automatically logs into a user account that isn't able to change much in the preference pane. How do I recover or change the administrator password?

The original owner told me to try a few passwords, none of which work to get logged in as admin.
Boot to OS recovery, internet recovery or on older systems, with a Mac OS X DVD, then there's an option to change passwords.



You can follow an how-to here.