Microsoft has written a Knowledge Base Article, Q196603, which provides recommended and alternative methods for repairing a Windows NT 4.0 - Service Pack 4 installation.

For repairing the registry, I prefer tip 505, as I keep 3 generations of my %SystemRoot%\Repair folder by scheduling an automatic update using tip 0072.

If I know what files I have to repair, I use the alternate boot to copy them from the most current source (Hotfix, expanded service pack or service pack CD-ROM, or WinNT CD-ROM).