1.Open the Window.
2.On the upper-left corner, click on the icon and select Advanced->Special Window Settings->Preferences.
3.Check No Border, on the drop-down list choose Force, then click the check box on the right.
4.Click Ok. That's it! Now, you could see the “Ok,” “Cancel” buttons.
Note: If you want to access this menu, press Alt-F3 on your keyboard.