Installing Active Directory Users and Computers for Windows 2008

From server manager, go to Features, then add

Expand:

• Remote Server Administration Tools
• Role Administration Tools
• Active Directory Domain Services Tools

and then check Active Directory Domain Controller Tools

it includes:

• Active Directory Users and Computers
• Active Directory Domains and Trusts
• Active Directory Sites and Services
• ...

Server 2008 R2 Instructions:

Under Role Administration Tools, expand

• AD DS and AD LDS Tools
• AD DS Tools
• AD DS Snap-Ins and Command-Line Tools.

Reference: http://serverfault.com/questions/108866/how-to-install-active-directory-users-and-computers-for-windows-2008