When you run the netdiag command on a Windows Server 2003 server, you may encounter the following errors:

    [FATAL] Could not open file C:\WINDOWS\system32\config\netlogon.dns for reading.
    [FATAL] Could not open file C:\WINDOWS\system32\config\netlogon.dns for reading.
    [FATAL] No DNS servers have the DNS records for this DC registered.
 

This is because the 32-bit version of netdiag, while supported by Microsoft, isn't able to locate the DNS file in a 64-bit installation.  To fix this issue, copy netdiag.exe from the Windows Server 2003 64-bit installation CD (SUPPORT\TOOLS\Support.cab) to C:\Program Files (x86)\Support Tools.