My network is a mix of Windows 2000 and Windows NT 4.0 servers and workstations. I want to migrate to Active Directory (AD), but I'm not certain how to begin. Should I upgrade my NT 4.0 PDC to Win2K? What will happen?

Starting the move to AD isn't overly difficult, but make sure you understand the effects and carefully plan the migration before you begin. I recommend that you read Douglas Toombs, "Migrating Domain Controllers to Windows 2000," February 2000, to get an idea about some of the hurdles. (For more information about tools that might help you move to AD, see Ed Roth, "NT-to-Win2K Migration Tools," September 2000, and Mark Minasi, Inside Out, "The Active Directory Migration Tool," July 2000.)

Having said that, I think that upgrading your PDC to Win2K Server is a good way to start your migration to AD. When you upgrade your PDC, the Win2K upgrade process will prompt you to install AD. You'll need to tell AD that you're running a mixed-mode environment. After you complete the AD installation, NT 4.0 clients and BDCs will still see the server as an NT PDC. However, when you add new Win2K servers or workstations, they'll join AD rather than the NT 4.0 domain (whether you want them to or not).

When I upgraded my network's PDC from NT 4.0 to Win2K, I was surprised by how easy the upgrade process was. After I installed AD, I opened the Microsoft Management Console (MMC) Active Directory Users and Computers snap-in and saw that all the NT 4.0 user and computer accounts had been pulled into AD. When I began configuring AD and adding new users and workstations, Win2K synchronized the AD objects with NT 4.0­compatible objects on my NT 4.0 BDCs. New users could take advantage of both AD and NT 4.0 resources.

AD makes the most sense for midsized or large companies because it simplifies navigation and administration, which can be tedious in large distributed environments; the payoff for small companies is minimal. However, if you're planning to upgrade to Microsoft Exchange 2000 Server or if you're adding new networks that require Exchange 2000, you need to push for an AD migration: To fully benefit from Exchange 2000's functionality, you must have AD. (For information about how Exchange 2000 relies on AD, see Tony Redmond, "Exchange 2000 Server over Active Directory," September 2000.)