Q. Why can I use only the NetBIOS domain name and not the DNS domain name to join a computer to a domain that's been upgraded from Windows NT Server 4.0 to Windows Server 2003 or Windows 2000 Server?

A. After you've upgraded an NT-based domain to Active Directory (AD), you should be able to use either the domain's NetBIOS name (e.g., savilltech) or its DNS name (e.g., savilltech.com) to join computers to the domain. If you can join a computer to the domain only by using its NetBIOS name, an incorrect DNS configuration might be the source of the problem. You can check a system's DNS configuration by entering the following lines at the command prompt. (The text that's enclosed in quotes represents messages that are displayed after you type the indicated commands.)

nslookup"Default Server: omega.savilltech.comAddress: 10.0.0.1"set type=srv_ldap._tcp.savilltech.com"Server: omega.savilltech.comAddress: 10.0.0.1""_ldap._tcp.savilltech.com SRV service location:priority = 0weight = 100port = 389svr hostname = omega.savilltech.comomega.savilltech.com internet address = 10.0.0.1"exit

Instead of _ldap._tcp.savilltech.com, enter _ldap._tcp, followed by your DNS domain name. If the nslookup command finds DNS records, your system's DNS configuration is probably correct. If nslookup finds no DNS records, check your DNS entries and, if they're correct, check the DNS server itself.

If your DNS configuration is in order, your domain controllers (DCs) might have the NT4Emulator registry entry enabled, which means they're emulating NT 4.0 DCs and thus won't respond to AD-style requests. You can test whether NT4Emulator is enabled on your DCs by configuring the neutralize NT4Emulator option on the client you're trying to join to the domain:

You don't need to restart the computer or log off; just try again to join the computer to the domain by using the DNS domain name. If the computer joins the domain successfully, you must either disable the NT4Emulator on the DCs or configure the NeutralizeNT4Emulator value on all machines on which you want to use the DNS name for the domain.