Old NT Service Packs
Q: Can I use UPromote with NT Service Pack 3 or earlier?
A: NT Service Pack 4 (released in 1998) changed the internal format of the password database. The general rule is that all domain controllers must run SP 4 or later. This is a well known issue with NT (KB Q197488). UPromote will work with earlier service packs, and it will warn you if it detects two servers with incompatible service packs.