请问怎样在DELPHI中实现显示桌面(30分)

如题

procedure TForm1.Button1Click(Sender: TObject);
begin
; keybd_event(91, MapVirtualKey( 91, 0 ), 0 , 0 );
; keybd_event(77, MapVirtualKey( 77, 0 ), 0 , 0 );
; keybd_event(77, MapVirtualKey( 77, 0 ), KEYEVENTF_KEYUP , 0 );
; keybd_event(91, MapVirtualKey( 91, 0 ), KEYEVENTF_KEYUP , 0 );
end;

多谢

var
; hDesktop : THandle;
begin
; hDesktop := FindWindow('Progman',nil);
; ShowWindow(hDesktop,SW_hide);
;//ShowWindow(hDesktop,SW_show);

end;