Can you boot from an external drive?

[sabre364]

The loaner computer I am using is running Tiger. My clone of my computer thats in service is Leopard, every time I hold option and try to boot from the external clone it tells me this computer needs to be restarted....can I just not boot from an external drive? whats going on?

 

[Drag'nGT]

Is it still cmd-opt-shift-delete to choose to boot from the external?
BTW, some Macs only boot from firewire (ppc). An Intel Mac should boot from firewire or usb.

 

[Shake 'n' Bake]

IIRC, you hold option key while booting then select the drive.

You also need a wired keyboard.

 

[miles01110]

What kind of connection are you using from the HD to computer? Didn't Tiger only support booting from FW?