Version 2.1 uses Silverlight to render certain videos, which requires the web server to serve XAML files. IIS 7 and higher should handle this fine, but earlier versions of IIS do not know what XAML files are.

To add the MIME types to IIS6:

1. Choose your website in IIS
2. Open the context menu and choose "Properties"
3. Select the tab "HTTP-Headers"
4. Click on the button labeled "MIME Types..."
5. If .xaml is not yet listed as a type, choose "New"
6. Enter the following description:

Extension: .xaml
MIME type: application/xaml+xml

7. Click "OK"