Windows Server 2008 introduces many improvements, and new features in the Active Directory infrastructure. Some of the most important features are:
- Flexible Password Policies
- Active Directory Auditing
- Read Only Domain Controllers RODC
In series of screencasts, we will demonstrate in a Step-by-Step fashion these new features.

In this screencast, we show you how to upgrade Active Directory domain to Windows Server 2008 AD DS by adding a new Windows Server 2008 Domain Controller.
- You can introduce your first Windows Server 2008 Domain Controller in Active Directory, by performing an in-place upgrade of an existing Windows 2003/2000 DC
- You can add a fresh installed Windows 2008 member server, and promote it as a DC.

There are a couple of very important considerations, that you should have in mind, before you proceed with your migration scenario.

● First, make sure that your Active Directory is healthy, and you have a perfect replication between the existing Domain Controllers. Using NetDiag, DCDiag, Repadmin from Windows Support tools could help you in this task. It is a very wrong approach to expect, that an in-place upgrade will solve your existing Active Directory problems.

● Second, you should have a good backup of your Domain Controllers, including the system state. If you have more than one DC (which is necessary) – backup all of them, or at least two DC.

● Check, whether you cover the hardware requirements.

● Check, and raise, if necessary, the Domain and Forest functional levels. You cannot upgrade directly from Windows 2000 mixed, or Windows Server 2003 interim domain functional levels.

● The first Windows Server 2008 Domain Controller in the forest must be a Global Catalog Server, and it cannot be a Read Only Domain Controller, RODC.

● Check the FSMO roles assignments. When you prepare the existing AD, you should run adprep /forestprep on the Schema operations master, and adprep /domainprep /gpprep on the infrastructure master.

In the following screencast, we demonstrate an upgrade of Windows 2003 Domain, by adding a new Windows Server 2008 Domain Controller.
If you are planning to perform an in-place upgrade of an existing Windows 2003 Domain Controller, then you could take a look at the following screencast:
Screencast - How to Upgrade Active Directory Domain to Windows Server 2008 AD DS Domain, In-Place 2003 DC Upgrade

If you intend to start from scratch, and create a new Windows 2008 domain, then you might find the following screencast helpful:
Screencast - How to Install a Windows 2008 Server Forest – Adding AD Domain Services Role