Procedure CreateWindows;
var
  wa, wb, wc, wd: TWndClass;
  hWindowParent, hWindowChild : Thandle;
  hMyChild : THandle;
begin

  if FindWindow('MyParent','') = 0 then
    begin

      with wa do begin
        lpszClassName := 'MyParent';
        lpfnWndProc := @MainWndProc;
        Style := CS_VREDRAW or CS_HREDRAW;
        hInstance := hInstance;
        hIcon := LoadIcon(0, IDI_APPLICATION);
        hCursor := LoadCursor(0, IDC_ARROW);
        hbrBackground := (COLOR_WINDOW + 1);
        lpszMenuName := nil;
        cbClsExtra := 0;
        cbWndExtra := 0;
      end;

      with wb do begin
        lpszClassName := 'MyChild';
        lpfnWndProc := @ChildWndProc;
        Style := CS_VREDRAW or CS_HREDRAW;
        hInstance := hMyChild;
        hIcon := LoadIcon(0, IDI_APPLICATION);
        hCursor := LoadCursor(0, IDC_ARROW);
        hbrBackground := (COLOR_WINDOW + 1);
        lpszMenuName := nil;
        cbClsExtra := 0;
        cbWndExtra := 0;
      end;

      Windows.RegisterClass(wa);


  //create main hwnd:
      hWindowParent := CreateWindowEx(WS_EX_TOPMOST Or WS_EX_TOOLWINDOW,
        'MyParent',
        nil,
        WS_POPUP,
        CW_USEDEFAULT, 0,
        0, 0,
        0,
        0,
        hInstance,
        nil);

  Windows.RegisterClass(wb);

  hWindowChild := CreateWindowEx(WS_EX_TOPMOST Or WS_EX_TOOLWINDOW,
    'MyChild',
    nil,
    WS_CHILD,
    CW_USEDEFAULT, 0,
    0, 0,
    hWindowParent,
    0,
    hMyChild,
    nil);

  end;
end;