This policy setting allows you to manage the loading of Extensible Application Markup Language (XAML) files. XAML is an XML-based declarative markup language commonly used for creating rich user interfaces and graphics that take advantage of the Windows Presentation Foundation.If you enable this policy setting and set the drop-down box to Enable XAML files are automatically loaded inside Internet Explorer. The user cannot change this behavior. If you set the drop-down box to Prompt the user is prompted for loading XAML files.If you disable this policy setting XAML files are not loaded inside Internet Explorer. The user cannot change this behavior.If you do not configure this policy setting the user can decide whether to load XAML files inside Internet Explorer.
Windows Components\Internet Explorer\Internet Control Panel\Security Page\Locked-Down Trusted Sites Zone
At least Internet Explorer 7.0