Hacking computers is generally unethical, but some hacking tools come in handy sometimes, like when you have an...
administrator account, but can't remember the password.
I've found a useful site for information on password resetting and hacking needs: http://www.petri.co.il/forgot_administrator_password.htm#1.
I've only had to use the top two (out of five) free utilities to get my clients' admin accounts unlocked. The site also provides links to each utility's home page with more detailed directions.
Note: As usual, back up your data before you use these.
For more information on passwords, see: How to crack a password.