If you new PC has a total failure, you'd presumably want to install Office on a new one; that's where my previous advice comes into play. Provided you've kept a copy of your Office Product Key (and, ideally, the installation files) you should be OK. You don't have to uninstall Office from the failed one and, as I said, there is no 'deregistration' mechanism.

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]