Windows 7 prompting for credentials when accessing SharePoint documents

Sympton
You are prompted to enter your credentials, even though the user account that you are using has sufficient permission to access this site.

For example, when you open a Microsoft Office file from a Microsoft Office SharePoint site by using 2007 Microsoft Office on a Windows 7-based client computer that has no proxy configured, you are prompted for authentication.

Solution
you have to create a registry entry. To do this, follow these steps:

1. Click Start, type regedit in the Start Search box, and then press ENTER.
2. Locate and then click the following registry subkey:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WebClient\Parameters
3. On the Edit menu, point to New, and then click Multi-String Value.
4. Type AuthForwardServerList, and then press ENTER.
5. On the Edit menu, click Modify.
6. In the Value data box, type the URL of the server that hosts the Web share, and then click OK.Note You can also type a list of URLs in the Value data box. For more information, see the “Sample URL list” section in this article.
7. Exit Registry Editor.
8. Restart the WebDAV service.
9. Open an elevated command prompt and type in net stop WebClient && net start WebClient
10. Reconnect to your SharePoint site.