Forgot Your Account Password
For Snow Leopard and earlier
For Lion/Mountain Lion
Boot to the Recovery HD:
Restart the computer and after the chime press and hold down the COMMAND and R keys until the menu screen appears. Alternatively, restart the computer and after the chime press and hold down the OPTION key until the boot manager screen appears. Select the Recovery HD and click on the downward pointing arrow button.
When the menubar appears select Terminal from the Utilities menu.
Enter resetpassword at the prompt and press RETURN. Follow
instructions in the dialog window that will appear.
Or see Reset a Mac OS X 10.7 Lion Password and
You can reset the password as follows:
To start, reboot in safe mode. At the prompt enter the following:
Press RETURN. If you receive this message: ** The volume (name_of_volume) appears to be OK then continue to the next command. If you receive this message: ***** FILE SYSTEM WAS MODIFIED ***** then repeat the above command until you receive the OK message. If you repeat the command seven times without receiving the OK message then you cannot repair the drive and should not continue.
/sbin/mount -uw /
Then, type in pressing RETURN after each:
netinfod -s local
You’ll be asked to come up with a new password. If you want to change a login’s password, substitute ‘root’ with the username. After that, enter