I meant APM, APF is a typo.

1. Insert system CD or DVD and boot holding down the C key to boot to the Mac OS X Installer.

2. The first screen will ask what language. Choose English and click Continue (or whatever it is.)

3. Next screen...if you have a mismatched Installer you'll get the message that you can't install on this hardware. Ignore that error message--but DON'T dismiss it, or the computer will reboot.

4. Pull down the Utilities menu (or, in a Leopard installer, I think it's the Apple menu--going from memory here.)

5. Choose Disk Utility if it's reformatting you're after. Or the password utility if that's your goal.

From there, you follow the bouncing ball.

I'm on the road for the next couple days so it'll take a little while to respond if you need clarification.