Error message when you run the Communications Server 2007 Validation Wizard to validate the Web Components Server: "Received a failure HTTP response.: HTTP Response: 401 Unauthorized"

To work around this behavior, use one of the following methods.

Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall the operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.

Method 1: Add the host names of the Group Expansion virtual server and of the ABS virtual server to the registry

To do this, follow these steps:

1. Click Start, click Run, type regedit, and then click OK.
2. In Registry Editor, locate the following registry subkey:
   
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\MSV1_0
3. Right-click the MSV1_0 registry subkey, point to New, and then click Multi-String Value.
4. Type BackConnectionHostNames, and then press ENTER.
5. Right-click BackConnectionHostNames, and then click Modify.
6. In the Value data box, type the host names of the Group Expansion virtual server and of the ABS virtual server, and then click OK.
   
   Note Make sure that you type each host name on a separate line.
7. Exit Registry Editor, and then restart the IISAdmin service.

Method 2: Disable the loopback check security feature

Warning This workaround may make a computer or a network more vulnerable to attack by malicious users or by malicious software such as viruses. We do not recommend this workaround but are providing this information so that you can implement this workaround at your own discretion. Use this workaround at your own risk.

Note If you do not want to disable the loopback check security feature, use Method 1.

To have us disable loopback check security for you, go to the "Fix it for me" section. If you would rather disable loopback check security yourself, go to the "Let me fix it myself" section.

Fix it for me

To disable loopback check security 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.

Let me fix it myself

To fix this problem yourself, follow these steps:

1. Click Start, click Run, type regedit, and then click OK.
2. In Registry Editor, locate the following registry subkey:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa
3. Right-click the Lsa registry subkey, point to New, and then click DWORD Value.
4. Type DisableLoopbackCheck, and then press ENTER.
5. Right-click DisableLoopbackCheck, and then click Modify.
6. In the Value data box, type 1, and then click OK.
7. Exit Registry Editor, and then restart the computer.