When doing a zone transfer from a NT 4.0 DNS server to a Windows 2000 DNS server it is imperative that the zone name be entered in 2 locations:
1) On the TCP/IP properties, Advanced, DNS tab. It is necessary to enter the complete zone name in slot titled "DNS suffix for this connection". It is also wise to choose "Register this connections addresses in DNS".
2) On the Network Identification Tab of your System Properties Page. You must go to Network Identification, Properties, More..., and input your zone name in the "Primary DNS Suffix for this computer" slot.
Failure to do this will cause failures in zone transfers. Sometimes the main forward lookup zone will transfer but not your reverse lookup zones or child domains. This causes the NT 4.0 DNS server to view your Windows 2000 DNS server as unauthorized even though you might allow zone transfers to anyone.