To the best of my knowledge you cannot boot from a USB external hard drive.
From time to time I do see postings indicating that this is possible if the
motherboard's BIOS supports this option, but I've yet to find a way to do
it. I've worked with a fairly wide variety of current motherboards but I've
been unable to find one that actually permits this capability.
The following is from Western Digital FAQs:
Question: Can I boot my computer using an external (FireWire, USB, Combo)
hard drive?
Answer: Western Digital does not provide technical support for booting your
computer using an external hard drive. BIOS manufacturers who design PC
system BIOS chips have informed Western Digital that it is not currently
possible to boot your computer with an external hard drive.
I have also queried Symantec Technical Support on this issue and here's the
response I received:
Thank you for contacting Symantec Online Technical Support.
You wanted to know if you could boot from a external USB drive that you have
cloned to using Norton Ghost.
The issue at hand would be whether the drive would be recognized in the boot
sequence of your system. To the best of my knowledge, there is no
motherboard that supports booting from external devices currently. This
really has nothing to do with Norton Ghost.
Using Symantec's Ghost 2003, I routinely clone my internal hard drives
(containing the Windows XP OS) to a USB external hard drive. I can
subsequently clone the external drive back to the internal one and the
internal drive will be bootable, however, as I've previously stated, I've
not been able to boot directly from the external USB drive.
Art