I am not sure what exact control you are asking about - you have asked about the RadWindow and at the same time your ticket was submitted for RadControls for Windows Forms. Would you please confirm that you meant RadWindow for ASP.NET AJAX?
As to the problem itself, in order to be able to help we will need some further information about your code and what exactly is wrong and under what browser the issue occurs, whether you use a custom skin or not, etc. In the common case, there is not a problem with the titlebar appearance as you can see in our online demos below:
What I suggest is to open a new support ticket and send us a sample reproduction demo with as detailed and many explanations and screenshot and information as possible - this will ensure that we will be able to help fastest and best.
the Telerik team