The process for changing an administrator's password is ordinarily the same as changing any other password. But what happens if you forget your administrator password? Under normal circumstances, you can't change a password without knowing what it was before.
Mac OS X provides two ways to reset a forgotten administrator password. Use the first, which is quicker and easier, if you (or someone else who can assist you) can access the administrator account used when Mac OS X was first set up. Use the second if the computer has only one administrator account or if the password to the original administrator account has been forgotten.
Although your Mac can have any number of administrators, one particular administrator account — the one that you created when you first installed Mac OS X or set up a new Mac — has a special status (even if you've since changed its password or other characteristics). The current password to that account — and only that account — can be used to reset the password for any other administrator account on your Mac.
If you have access to the original administrator account on the Mac or can enlist the aid of someone who does, follow these steps to reset the password of another administrator account:
Choose System Preferences to open System Preferences and then click Accounts ...