system.dat ; user.dat

I don't think they exist under NT4. Your personal settings are contained in c:\winnt\profiles\%yourprofile%\ntuser.dat and all other files+folders in that directory.

I think machine-specific keys are in c:\winnt\system32 in files named system, security, software.

System.dat and user.dat files are the registry files for a windows 9.x system.
Windows NT does not have these files. The registry is contained in other files. However, I would not recommend accessing those files directly. For any user informationand profiles. The previous answer states where the information is kept.

All the system registry information is located in %systemroot%\Repair. This is also the information used to repair the installation (also contained in ERDisk). It can be updated whenever you want running "rdisk -s"

This question was closed by the author