You receive error 401.1 when you browse a Web site that uses Integrated Authentication and is hosted on IIS 5.1 or a later version
Solution : http://support.microsoft.com/kb/896861
Method 1: Specify host names (Preferred method if NTLM authentication is desired) To specify the host names that are mapped to the loopback address and can connect to Web sites on your computer, follow these steps:
Set the DisableStrictNameChecking registry entry to 1. For more information about how to do this, click the following article number to view the article in the Microsoft Knowledge Base:
281308 Connecting to SMB share on a Windows 2000-based computer or a Windows Server 2003-based computer may not work with an alias name
Click Start, click Run, type regedit, and then click OK.
In Registry Editor, locate and then click the following registry key:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\MSV1_0
Right-click MSV1_0, point to New, and then click Multi-String Value.
Type BackConnectionHostNames, and then press ENTER.
Right-click BackConnectionHostNames, and then click Modify.
In the Value data box, type the host name or the host names for the sites that are on the local computer, and then click OK.
Quit Registry Editor, and then restart the IISAdmin service.
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