This article explains how the Domain Controller Diagnostic Utility can be used to troubleshoot problems with the Active Directory. The Domain Controller Diagnostic Utility has been a part of Windows for quite some time now. For this article, we’ll be working with the version of this utility that comes with Windows Server 2008. Most, if not all of the features that’re talked about are also available in the Windows Server 2003 SP1 version. DCDIAG existed prior to Windows Server 2003 SP1, but many of the commands that are available today were first introduced in Windows Server 2003 SP1. You can access the Domain Controller Diagnostic Utility by running the DCDIAG command from a Windows command prompt.