If I create a local hosts file entry (like fileserver for example) which points back to my local machine's ip address and then attempt to access a shared folder on my local machine (from windows explorer) from the same local machine using that same host name entry i.e. \\fileserver , I am always presented w. an authentication challenge that fails even though I am already logged on to the same machine. This happens even if I present the proper credentials (domain\username and password) to the authentication challenge. The pc is not technically part of any domain (local domain). TCP/IP name reslution via the local host file works just fine, as "ping fileserver" returns a reply from the local host as expected. If I try to access the same shared folder via \\localhost, or \\127.0.0.1, or the host's actual ip address \\192.168.1.102 no challenge is presented and the shared folder is completely accessible. This can also be reproduced on any other Windows 7 machine This is very strange. Thanks for any enlightenment you could share.

Is this just a random obersavtion/query or is it causing something to fail in your environment? Sumesh P - Microsoft Online Community Support

Disable the authentication loopback check <script type="text/javascript">// <![CDATA[ loadTOCNode(3, 'resolution'); ]]></script> Re-enable the behavior that exists in Windows Server 2003 by setting the DisableLoopbackCheck registry entry in the HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa registry subkey to 1. To set the DisableLoopbackCheck registry entry to 1, follow these steps on the client computer: Click Start, click Run, type regedit, and then click OK. Locate and then click the following registry subkey: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa Right-click Lsa, point to New, and then click DWORD Value. Type DisableLoopbackCheck, and then press ENTER. Right-click DisableLoopbackCheck, and then click Modify. In the Value data box, type 1, and then click OK. Exit Registry Editor. Restart the computer. Note You must restart the server for this change to take effect. By default, loopback check functionality is turned on in Windows Server 2003 SP1, and the DisableLoopbackCheck registry entry is set to 0 (zero). The security is reduced when you disable the authentication loopback check, and you open the Windows Server 2003 server for man-in-the-middle (MITM) attacks on NTLM. http://support.microsoft.com/kb/926642 Sumesh P - Microsoft Online Community Support