there is no "shadow" file, unless you are referring to Vista's Volume shadow copy, but that only duplicates files- I'm not sure if it duplicates system files though.
Or- you might mean a file with the hidden and system attributes. But from what I understand passwords are stored in the registry in some way (obviously not plaintext).
Even in such a case, replacing the hard drive means such files are no longer existent.
In this case the OP has been assured multiple times that data stored in the CMOS does not contain sensitive data, but for some reason persists the issue.