procedure TForm1.Button1Click(Sender: TObject);
var buff: array [0..127] of Char;
      Wnd: hWnd;
begin
  ListBox1.Clear;
  Wnd := GetWindow(Handle, gw_HWndFirst);
  while Wnd <> 0 do
  begin {Не показываем:}
    if (Wnd <> Application.Handle) and {-Собственное окно}
    IsWindowVisible(Wnd) and {-Невидимые окна}
    (GetWindow(Wnd, gw_Owner) = 0) and {-Дочернии окна}
    (GetWindowText(Wnd, buff, sizeof(buff)) <> 0){-Окна без заголовков}
    then
    begin
      GetWindowText(Wnd, buff, sizeof(buff));
      ListBox1.Items.Add(StrPas(buff));
    end;
    Wnd := GetWindow(Wnd, gw_hWndNext);
  end;
  ListBox1.ItemIndex := 0;
end;