1. After retyping your password very carefully at least twice to make sure you just didn’t mistype it, you’ll need to haul out your OS X install disk,
2. Insert it into your Mac and restart holding down the C button.
3. After selecting your language of choice, in the menubar, select Utilities > Reset Password.
4. Follow the directions and there you go. Just try not to get a lobotomy after resetting it!
5. Enjoy......