From: John Cuccia 

On Mon, 28 Feb 2005 21:31:58 -0500, "Geo"  wrote:

>"John Cuccia"  wrote in message
>news:7rb721hadedqb22or7m3uh8e73aobb2dng{at}4ax.com...
>
>> If you prefer, you can install NT4 on the new machine, configured as a
>> BDC, then promote it to PDC, then upgrade it.
>
>Excellent suggestion.
>
>> If you run your AD domain in Windows 2000 Server mixed mode (the
>> installation default), you can leave the old NT4 server on-line as a
>> BDC for as long as you like.
>
>It doesn't work very well, the two domain models are so different that it's
>just not a stable way to do things. The worst part is the PDC has to be NT4,
>you can't have an NT4 BDC with a W2K PDC.

True, the environments are different, but, yes, you can have an NT4 BDC
that works in an mixed-mode AD environment (that's what mixed-mode is for).
 One of the FSMO roles assumed by a W2K or W2K3 domain controller is
"PDC Operations Master".   Note the bullet points in the
excerpt below.

http://www.microsoft.com/technet/prodtechnol/windows2000serv/deploy/cookbook/co
okchp2.mspx
The Active Directory installation process copies the contents of the
Windows NT account database and the Security Accounts Manager (SAM) into
Active Directory. These objects are the security principals (user accounts,
local and global groups, and computer accounts).

As soon as the process upgrades the PDC and installs Active Directory, the
domain is running in Windows 2000 mixed mode. (For a fuller description,
see the section "Mixed Mode and Native Mode" below.) The former
PDC now holds the role of the PDC operations master in the Active Directory
domain.

From this point on, the Windows 2000 Server PDC operations master uses
Active Directory to store objects. It is fully backward compatible because
it exposes the data as a flat store to Windows NT BDCs during replication.
This manifests itself in a number of ways:

• The PDC operations master appears as a Windows 2000 domain controller to
other computers running Windows 2000 and as a Windows NT PDC to computers
that are not yet upgraded.

• You can still use the PDC operations master to create new security
principals and to replicate these changes to the Windows NT Server BDCs.

• Windows NT and Windows 9x workstations can use the PDC operations master
as a possible logon server.

• If the Windows 2000 Server PDC operations master goes offline or
otherwise becomes unavailable and no other Windows 2000 domain controllers
exist in the domain, then you can promote a Windows NT BDC to PDC.

--- BBBS/NT v4.01 Flag-5