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;