Thank's for your help about Radwindow Theme.
Now I have another question. I can not setting my custom Icon in the Window Title bar....
I tried to set the 'Icon' attribute:
This is not right way to set the Icon of the RadWindow. First of all you should change the IconTemplate of the RadWindow control, because the default one contains the default Icon. As we know this is not expected we changed this behavior and you won't need to do that any more.
To make this work in the current version do the following: