If you have lost a password to an OS X user account on your Apple Macintosh, this will help you reset it. This guide works for all apple computers including but not limited to MacBook, MacBook Pro, iMac, Mac Mini, Mac Pro, and MacBook Air.
Power it on, and hold Command (Apple Button) + S at the same time.
Substitute john for the username you wish to reset.
You’ll now be prompted to enter a new password for john twice. Once to enter it, the second time to confirm.
You can now login to that user account with the new password.
2011-08-24: HTML error fixed causing vital information in step one to be omitted from view.