1. Click on the Start button and type in "Internet Information Services (IIS) Manager", and open it.
2. Expand the menu on the left and click on Application Pools. Verify that the CasaTunesAppPool is pointing to the v4.0 .NET framework.
3. Next, expand the left menu again and under "Default Web Site", click on CasaSetup. On the right side, click "Advanced Settings..." Verify that CasaSetup is pointing to the CasaTunesAppPool. Repeat these steps for CasaTunes on the left menu.