Access Denied on Orchard CMS theme files on IIS 7

Today I'm working on moving an Orchard CMS site from an IIS6 server to an IIS7 server.  I copied the folder over to its new home and used "Add Application" to set the folder up.  I added the Application Pool user (use "IIS AppPool\AppPoolName" as the user in the security dialog -- see http://stackoverflow.com/questions/7334216/iis7-permissions-overview-applicationpoolidentity) and voila, everything worked!  Well -- almost everything -- none of my themes' css were showing up.

In the browser network tab I could see that all of the css files were getting a 302 error -- "Access Denied".  Strange!

I found that in the IIS7 Authentication panel, the Anonymous Authentication was set to use the default IIS "IUSR" instead of my application pool identity.  The dialog:

Changing it to "Application pool identity" did the trick!