This is called Firewire Target disking. Plug the two computers into each other with a FireWire cable, then start on up Holding T. From there you will see it mounted on the other computer's desktop as an external drive.
This has been posted before, but it could be hard to come up with search terms if you didn't know what it was called...so I'll let you off the hook.....this time.
This has been posted before, but it could be hard to come up with search terms if you didn't know what it was called...so I'll let you off the hook.....this time.