This policy setting allows you to manage the loading of XAML Browser Applications (XBAPs). These are browser-hosted ClickOnce-deployed applications built via WinFX. These applications run in a security sandbox and take advantage of the Windows Presentation Foundation platform for the web.If you enable this policy setting and set the drop-down box to Enable XBAPs 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 XBAPs.If you disable this policy setting XBAPs 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 XBAPs inside Internet Explorer.
Windows Components\Internet Explorer\Internet Control Panel\Security Page\Locked-Down Trusted Sites Zone
At least Internet Explorer 7.0