Mac OS X Install CD:Applications:Utilities
When you first run Open Firmware Password, you are presented with a window that says "The Open Firmware password is used to prevent others from starting your computer with a different disk. This makes your computer more secure."
WARNING!!!!!
The Mac Observer urges caution in using this or any firmware password application. Misuse could result in an unbootable system or worse. Firmware operates at the lowest level of the Mac. The data does not reside on any hard drive, so a reformat would be useless in reversing any misfortune. In Appleis case, caution is especially warranted since the utility includes no documentation or help files.
To add or change the password, you must click on the lock symbol in the lower left of the window and enter an administratoris password (see image).