When you use RadWindow to show an external content page, RadWindow uses an IFRAME and shows the content page in that IFRAME - content page's code does not exist in the parent page. If you use RadWindow as a controls container
however, the content of the window is rendered on the same page.
I hope this information helps. If you still experience problems, please open a support ticket and send a small sample application that shows the problem - we will check it and do our best to help.
the Telerik team