Migrating from a Windows NT 4.0 domain to an Active Directory based Windows 2000 Server or Windows Server 2003 domain can be a relatively painless process. That is if you take a few precautions. First and foremost, always perform a full backup before making any significant system or infrastructure changes to your environment. Second, plan out your alterations. Review your plans to ensure that you haven't overlooked anything significant. Finally, implement your changes with an eye for problems. If you see issues looming on the horizon, take steps to avoid or minimize them.

One of the most common infrastructure improvements is to migrate from Windows NT 4.0 to an Active Directory domain. The central aspect of this task is to upgrade the domain controllers. Once the domain controllers are all upgraded, the transition is pretty much complete. Any remaining member servers can remain as is or be upgraded as well. But the alteration of member servers has no real effect on the nature of the domain.

Here are some rules of thumb to follow when performing a domain controller upgrade:

1. Always have at least two BDCs in each domain to support and backup your PDCs.
2. Take the PDC offline.
3. Upgrade the PDC to Windows 2000 Server or Windows Server 2003.
4. Return the upgraded domain controller to the network.
5. Once interoperability is established and the stability of the network confirmed, upgrade the two BDCs while connected to the domain.

The beauty of this process is if the upgrade to the PDC fails, the BDCs are able to maintain the existing Windows NT 4.0 domain environment. If the PDC cannot be returned to the network, upgraded or not, one of the BDCs can be promoted and the process attempted again. Plus, upgrading the PDC while offline will ensure that no changes to the domain are made and the network's security and accounts database will not be subject to corruption during the upgrade process.

James Michael Stewart is a partner and researcher for Itinfopros, a technology-focused writing and training organization.