One NTUSER.DAT for each user on the machine, some templates and repair.
C:\Documents and Settings\Administrator
C:\Documents and Settings\Default User
C:\Documents and Settings\LocalService
C:\Documents and Settings\NetworkService
C:\Documents and Settings\Your Name Here\NTUSER.DAT
C:\WINDOWS\repair
All hives are stored in %systemroot%\SYSTEM32\CONFIG. Except
HKEY_CURRENT_USER. That's stored in C:\Documents and Settings\Name Here.
The major hives and their files are as follows:
If your interest is to back it up and keep copies safely stored, it's better
to use Backup to do a System State backup. That backs up the Reigistry and
ALL other relevant things needed to re-establish the system to operational
value. You also get to create a log file when the process completes, which
is a text file and can be read in any editor.
The System State backup option is in the backup wizard, first or second
dialog box, not sure which.