When you install the Directory Services for Microsoft Windows network it will feel like you install the heart of something that will become alive after you reboot the server. Since Windows 2000 the Directory Services has been the core component of the Windows network. 

Couple minutes ago I finished my first domain controller installation for AD DS (Active Directory Domain Services) for Windows Server 2008 RTM. The dcpromo wizard has couple new steps; check out my screencast of the AD DS installation.

Windows 2008 AD DS has the following improvements :

Read-only domain controller (RODC)
Staged installation of an RODC
RODC filtered attribute set
Administrator role separation
Improved installation wizard
Generate secure installation media
Restartable AD DS
Auditing AD Ds changes
Fine-grained password policy
Dynamic MAPI ID Support
Data mining tool