Yo, problem is solved. W2k has 3 backups of system file stored. One in .\system32\config folder, the system.alt file and 2 in %windows_home%\repair folder i.e regback and system. By renaming/replacing the corrupt system file with one of these files, the problem was solved. System.alt is most recent, after that regback and finally system. Regback worked for me. I only lost some registry entries and had to install some drivers again.

Topic can be closed.

Greetings

Thoth