Error message when you try to join a Windows Vista-based client computer to a top level domain (TLD) that has a purely numeric suffix: "An Active Directory Domain Controller for the domain <DNS domain name> could not be contacted"

When you try to join a Windows Vista-based client computer to a top level domain (TLD) that has a purely numeric suffix, the Windows Vista-based client computer cannot join the domain. Additionally, you receive the following error message: Note An example of a purely numeric suffix is "contoso.2003."

When you click Details, you receive the following error message: If you try to join the domain by using the NetBIOS name of the domain, you are prompted for domain credentials. In this case, the client computer still cannot join the domain. Additionally, you receive the following error message:

This article helps you fix the problem. To have us fix this problem for you, go to the “Fix it for me” section. If you would rather fix this problem yourself, go to the “Let me fix it myself” section.

To fix this problem automatically, click the Fix this problem link. Then click Run in the File Download dialog box, and follow the steps in this wizard.



Note This wizard may be in English only; however, the automatic fix also works for other language versions of Windows.

Note If you are not on the computer that has the problem, you can save the automatic fix to a flash drive or to a CD, and then you can run it on the computer that has the problem.

Now go to the "Did this fix the problem?" section.

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base: To fix this problem, add the ScreenBadTlds registry entry. Adding this registry entry prevents the client computer from performing the test to determine whether the top level domain is supported.

To add this registry entry, follow these steps.

1. Click Start
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   , type regedit in the Start Search box, and then press ENTER.
   Note If you are prompted for an administrator password or for confirmation, type the password or provide confirmation.
2. Locate and then click the following registry subkey:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Dnscache\Parameters
3. On the Edit menu, point to New, and then click DWORD Value.
4. Type ScreenBadTlds, and then press ENTER.
5. Right-click ScreenBadTlds, and then click Modify.
6. In the Value data box, type 0, and then click OK.
7. Exit Registry Editor.

Now go to the "Did this fix the problem?" section.

Check whether the problem is fixed. If the problem is fixed, you are finished with this article. If the problem is not fixed, you can contact support.

This behavior is by design.

This issue does not occur with domain names that have numbers and letters in the domain suffix. For example, this issue does not occur with domain names that resemble the following:

• contoso.200three
• contoso.two003

Also, this issue does not occur with domain names that have numbers in the domain prefix. For example, this issue does not occur with domain names that resemble the following

• 2003.Contoso
• 200three.Contoso

When this issue occurs, all Domain Name System (DNS) records are returned correctly when the computer is joining the domain. In a network trace, correct records are queried for and returned. Therefore, DNS is fully functional and is not part of this issue.