Unable to Join Computer to Active Directory - Single Name Domain

 Azure Domain Services

Issue 

Our DC was a Windows NT 4.0 Server Single Label Domain that was migrated to Windows Server 2003 as a Single Label Domain, which was eventually migrated to Windows Server 2008 R2 carrying the Single Label Domain.  The issues stem from DNS not working well with Single Label Domains and I found a really great article outlining Single Label Domains and we are exhibiting many of the issues outlined in the article.

http://blogs.msmvps.com/acefekay/2009/11/12/active-directory-dns-domain-name-single-label-names/

Resolution - 

Work around to our Single Label DNS Domain issue that allows remote computers to join the domain.

In the registry of the client computer you are trying to join to the Single Label Domain add the following registry entry:

Go to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\Netlogon\Parameters

Create a REG_DWORD (32-Bit) Value called AllowSingleLabelDnsDomain

Change the Data Value of the newly created registry entry from 0 to 1

Reboot the computer and you will be able to join your remote computer to the Single Label Domain.