After you shut down your MacBook, upon pushing the on button, press the command key plus the "s" key this will enter the Bios style menu...
BE CAREFUL OF SPACES, END PARAGRAPH(enter key), and CAPS, or it will stick in coninual route.
As soon as the screen gets to the line stating, root#: , and has the curser available for typing/ Type:
mount -uw /
rm /var/db/ .AppleSetupDone
shutdown -h now
Then your apple will shut down, after you push the on button, the MacBook laptop should be accurately set as if you have a brand new apple laptop, it is very easy and quick, just make sure you pay attention! :-)
note this is for mac running mountain this method should be performed if no disk is available