The RadWindow does not have shadow at the moment however we have plans to enable it. We are currently researching a way to add it without damaging the CPU. We will turn back the old Windows7 look and feel for the service pack. The fix will be also available in one of the upcoming releases. If you could use the window in its current state until the SP1 the design will be back to normal.
I am sorry for the inconvenience. If you really need a fix I could provide the RadWindow's Windows7 XAML with less transparent background but it will still be without shadow. I would recommend you to upgrade to the SP1 once it is released.
the Telerik team
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