unfortunately we do not offer general tech support here at O'Reilly. If it was a question about a lesson or example in one of our books we'd be happy to help.
If the external drive came with software, I would recommend referring to it's documentation or support site to get the definitive answer that would best suit your backup / restore needs.
Also, you can find a lot of useful information about the backup / restore feature of Windows 7 on
They have an extensive set of articles on the topic. Sorry we couldn't be of more help.
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