Problem:

When trying to edit a Microsoft Office document from a SharePoint Site on a Windows Vista computer, you get the following error: “Unknown Error Trying to Lock File”.

Cause:

Windows does not automatically authenticate the user.

Solution:

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1. Locate and then click the following registry [HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WebClient\Parameters]
2. On the Edit menu, point to New, and then click Multi-String Value.
3. Type AuthForwardServerList, and then press ENTER.
4. On the Edit menu, click Modify.
5. In the Value data box, type the URL of your site. For multiple URLs, enter each URL on a new line. You can also create wild cards to include all .com’s, .net’s, etc…
   Example:

   http://mysite.com
   *.com
   *.net

6. Click OK
7. Restart your WebClient Service and there you go.

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FYI:

After many, many, many hours of searching I found this 100% solution.

Creating a network location to the root of your site temporarily fixes this issue, but every time your webclient service gets restarted, you have to open your network location again so that you can authenticate to the site.

The solution that is provided with this blog post is a 100% solution. The only problem is having to update the registry on all of the computers that needs this functionality.

Downloads:

AuthForwardServerList.zip

Download 

The .reg file includes the wild cards *.com, *.net, *.biz, *.org
It must be run with administrative privileges.

Code:

Registry Code

Windows Registry Editor Version 5.00
 
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\services\WebClient\Parameters]
"AuthForwardServerList"=hex(7):2a,00,2e,00,63,00,6f,00,6d,00,00,00,2a,00,2e,00,\
6e,00,65,00,74,00,00,00,2a,00,2e,00,69,00,6e,00,66,00,6f,00,00,00,2a,00,2e,\
00,6f,00,72,00,67,00,00,00,2a,00,2e,00,62,00,69,00,7a,00,00,00,00,00

Copy the code above and paste it into notepad. Save the file as AuthForwardServerList.reg. Run the file as administrator.

Links:

Below are the two sites where I found this solution.

http://www.portalsolutions.net/Blog/Lists/Posts/Post.aspx?ID=27

http://lindaleechapman.spaces.live.com/blog/cns!F1562A7E3898DAB2!226.entry