GWindowsを使ってWindowを表示してみました。(Win2000)
GWindows url: http://www.adapower.com/gwindows/

--
-- wintest.adb
--

with GWindows.Windows.Main;
with GWindows.Application;

procedure WinTest is
use GWindows.Windows.Main;
Top: GWindows.Windows.Main.Main_Window_Type;

begin
Create (Top, "Hello World");
Size (Top, 300, 100);
visible (Top);
Gwindows.Application.Message_Loop;
end;