I think that Brody is only referring to the normal administrative password. In the event that you ARE dealing with an open firmware password, and his methods don't work, here is something you can try... it's a bit of work, because open firmware password is meant to make the computer extra secure.
Note: I take no responsibility if anything goes wrong if you use the methods listed below. They should only be used as a last resort if you can't get the password from the previous owner... and make sure you try Brody's suggestion first.
This is copied from:
http://www.computerworld.com/printthis/2005/0,4814,103889,00.html
******************Bypassing Open Firmware Security
If you forget the Open Firmware password for a computer, or if someone else sets one before you do, you can reset the Open Firmware settings to their defaults (no password and the none security mode). If other Open Firmware settings have been changed, this might reset them as well. As I said, it's a cumbersome process, so you'll want to avoid having to do it.
First, open the computer and either remove or install RAM. What you need to do is change the amount of RAM that's installed in the computer, so simply moving modules around won't do the trick. Reboot the computer with the changed amount of RAM and zap the PRAM. (Changing the installed RAM allows you to use the command-option-P-R key combination to zap the PRAM, regardless of the Open Firmware security mode, which removes the password.) Then boot into the Open Firmware prompt and use the set-defaults command. This should reset all Open Firmware configurations to the default settings. Use the reset-all command to reboot with the new settings, after which you can set a new password and security mode (either directly through the Open Firmware prompt or using another tool). Restore the original amount of RAM in the computer.
The ability to get around Open Firmware like this is a key reason to ensure that computers are physically secure. This process won't work unless you can get to the RAM inside the computer.
Unfortunately, it's possible to extract the Open Firmware password through other methods: mSec developed a Mac OS 9 tool called FWSucker after the introduction of Open Firmware simply to prove that it could be done. Apple restricted the use of the tool with Mac OS 9.2, and to date there is no corresponding Mac OS X native tool. However, it''s possible to extract the Open Firmware password from the nvRAM chip that holds all Open Firmware data on a Mac's motherboard. With that in mind, you should use managed preferences, Mac Manager settings or Mac OS X local user-access settings to restrict users to a list of known applications. That would help prevent users from running such a tool, should one be developed.
Ryan Faas is the network administrator and offers consulting services specializing in Mac and cross-platform network solutions for small businesses and education institutions. He is co-author of Troubleshooting, Maintaining and Repairing Macs (Osborne/McGraw-Hill, 2000) and of the forthcoming Essential Mac OS X Server Administration (O'Reilly, 2005). He can be reached at ryan_faas@yahoo.com.
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By the way, I would recommend against using FWsucker, and it probably wouldn't work anyway since Apple supposedly "blocks" it from running now.
