NT 4.0 adding new user

Are you limiting your user names to 15 characters, as NETBIOS will truncate anything over 15 characters? If all your usernames start with the same 15 characters, then that could be the problem. Also, if you recently deleted a bunch of user accounts and are adding them back in, it is possible that the old objects haven't fully purged out of the SAM database and still exist, giving you the error you see. You won't be able to call MS on this problem, but I would suggest you do a google search to see if you can find a solution. I haven't touched NT 4.0 in over 5 years and don't really recall much about it.

Everything was fine in synching with the BCD until a week ago. Now the tape backup program on the PDC is stating "Windows Registry - cannot copy". I have had problems with the backup program a few months ago.

When my tape backup reported that it could not copy the registey I deleted the Yosemite 7.X software. I had crashed it's own registry of backups months before and I fixed it via their instructions. The backup tape software "locked" the file to be copied and never released it. Hence I could not make any changed by adding users. After removing the software, I rebooted and I added those two users and the BDC can