IIS 7.5 Virtual Directory getting Unauthorized: Access is denied due to invalid credentials

I have a web application that is trying to access images from a shared folder on a different server.

In my web app, I created a new virtual directory. The alias is QCPhotos and the path is \alta\QCPhotos. Alta is a different server than my web server, which is Brighton.

I am getting the error:

401 - Unauthorized: Access is denied due to invalid cred开发者_StackOverflow中文版entials. You do not have permission to view this directory or page using the credentials that you supplied.

In trying to debug, on the Alta server, I have given the Everyone user full access to this folder. I also gave {domain}\Brighton$ full access to the folder.

I turned on Directory Browsing, and that seems to work fine. I can list the contents of the folder, but as soon as I click on a jpg image, this error comes up.

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Well, I'm still not sure why it wasn't letting me access, but I created a domain user acct named QCPhotos. I gave that user read permissions on the folder, and then set the virtual directory to use this user in IIS. This fixed my problem.