reference:http://technet.microsoft.com/en-us/library/cc776854(WS.10).aspx

This is for my use.  It is from the link above.

Domain Controller Diagnostics Tool (dcdiag.exe)

Applies To: Windows Server 2003 with SP1

What does DCDiag.exe do?

This command-line tool analyzes the state of one or all domain controllers in a forest and reports any problems to assist in troubleshooting. DCDiag.exe consists of a variety of tests that can be run individually or as part of a suite to verify domain controller health.

Tool Requirements

• Except as noted below, all commands in DCDiag can be run on Windows XP Professional and Windows Server 2003 family (member servers and domain controllers).