case WM_CREATE:
		{
			hOption = CreateWindowEx(WS_EX_TRANSPARENT,
			"button",
			"Beenden",
			WS_CHILD | WS_VISIBLE,
			0, 0, 0, 0,
			hWnd,
			NULL,
			((LPCREATESTRUCT) lParam) -> hInstance,
			NULL);

			return 0;
     		 }

		case WM_SIZE:
		{
			MoveWindow(hOption, 100,400,600,75,TRUE);

			return 0;
		}

Und das sagt msdn dazu (was mir bei der Lösung des Problems aber nicht wirklich weitergeholfen hat):

WS_EX_TRANSPARENT Specifies that a window created with this style is to be transparent. That is, any windows that are beneath the window are not obscured by the window. A window created with this style receives WM_PAINT messages only after all sibling windows beneath it have been updated.