Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
I know there is cause I have done it. Basically you have to type some code in, while in single user mode. I learnt this from having password reset issues. Hopefully a guru around here will know how to do it.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.