In the last NT installation I worked on we operated on the
understanding that a "disaster recovery" must assume a total loss of
the data centre.  We therefore, stored all installation media, and a
monkey sheet documenting all prompts issued and replies given off
site.  The assumption was that our hardware vendor would provide new
equipment in a comparable configuration to the lost machine.

Given the above a bootable restorable image was not appropriate (the
hardware would not be identical).  However, since the CD was
installed, patches have been applied to various system components.  It
remains necessary to be able to rebuild the underlying software to the
level in use when the disaster happened.

Our installation was strictly for SAP R/3 - there were no NT level
users defined and therefore not too many big issues relating to most
of the registry.  The interesting part with SAP though is that you
install once at what ever release level you choose but thereafter only
ever do an upgrade.  The supplied upgrade media does not provide the
capability of an install and, furthermore, if you do obtain the
installation media for you new release, the results of an upgrade are
not always identical to the "equivalent" installation.  For SAP,
therefore, it is necessary to be able to restore the executables and
other directories as of the point of failure.  This process does
require resyncing of those parts of the registry.

I suspect that SAP is not the only application for which this, or
another similar issue, is true.  The need to merge parts of the
registry back from a backup does exist.

Murray Nicholas
IT Systems Consultant
Galeforce Information Services Pty Ltd
email:  murray AT galeforce.bu.aust DOT com