Q: I have a mac with OX X 10.6.8  and have lost / forgotten the admin password what can I do???

You could start the computer from the installer DVD media disc and choose options in

the menu options, such as Utilities and other items; among them is a cue to reset the

password. In some vintage OS X installer discs, (when used to boot the computer) a

few other options appear in the drop-down menus that can be helpful.

You could start with the C key held, and keep holding it down for quite a time, while

waiting for the computer to try to run from the reduced OS X bits on the DVD. Or

you may choose to try the D key to see if any other volume of OS X can be found

on startup and choose (the DVD) that would do the correct job of allowing you to

change the password. Easiest with the install DVD, harder without it.

•Resetting a Forgotten (lost) Account Password - Mac OS X 10.6 & Before:

https://kb.wisc.edu/page.php?id=3853

Five ways to Reset a Lost admin Password: (see choice #3 for using DVD)

http://tidbits.com/article/14437

Another way without the install DVD, uses a command-line or single-user mode:

Snow Leopard 10.6 password reset, no disk method

This also is where one would be able to Installer a fully new OS X, so be careful to

choose the menu options and not the main installer, or disk utilities that can also be

used to ready a replacement hard drive or a second one for a new installation of OS.

Some keychain passwords and other items may need attention, so as to access

other functions that may have been set there. I try to not commit all my passwords

to the Keychain, and so seldom have need to use it.

Hopefully this helps somewhat.

Good luck & happy computing!