static extern uint ArrangeIconicWindows(IntPtr hWnd);

The ArrangeIconicWindows function arranges all the minimized (iconic) child windows of the specified parent window.

An application that maintains its own minimized child windows can use the ArrangeIconicWindows function to arrange icons in a parent window. This function can also arrange icons on the desktop. To retrieve the window handle to the desktop window, use the GetDesktopWindow function.