one of the best ways to backup/restore reg hives is w/ ERUNT.

http://www.larshederer.homepage.t-online.de/erunt/

runs from inside windows, not rec-console, so your current hives must be
sound enough to boot and then perfrom the "restore". of course you can
copy over the erunt backups by hand using rec-console, _IF_ you've relaxed
its file-access restrictions in the reg:

http://www.jsifaq.com/SF/Tips/Tip.aspx?id=7974

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FWIW,

in \windows\repair are the system's archived hive files, the classic
restore-from location. but these are placed there by windows setup, and
on many systems are as old as the setup itself (ie, pretty worthless).
however, doing a ntbackup "system state" type backup will update these
copies w/ the latest. [W2k used to have a quickie app that did this, but
it's gone in xp]. You might want to consider running ntbackup
occasionally because of this...