booting to read a firewire connected computer

If you just want to be able to read files off the target computer's hard drive, you boot your host computer normally, and on the target computer, attach a keyboard and reboot with the T key held down.

If you want to be able to boot the host computer from the target's hard drive, again boot the target Mac with the T key held down, and reboot the host computer with the Option key held down. You'll be able to choose the firewire-attached drive from the boot panel. This will work provided that the target computer has an OS that the host can boot.

Matt