Try the code below and then re-size the window. You will notice the icon shrinks to the size of the control (which is correct). Though I am interested to know what message should I used so this is done automatically? I know I can use WinMove() but that's a little hacky!   #include <GUIConstantsEx.au3> #include <WinAPI.au3> #include <WindowsConstants.au3> #include <WinAPIShellEx.au3> Global Const $STM_SETIMAGE = 0x0172 Example() Func Example() Local $hGUI = GUICre