procedure TForm1.FormHide(Sender: TObject);
begin
	Application.Minimize;
end;

procedure TForm1.FormShow(Sender: TObject);
begin
	Application.Restore;
end;

procedure TForm1.ApplicationEvents1Minimize(Sender: TObject);
begin
	Hide;
end;

procedure TForm1.OnAppCallBack(var Message: TMessage);
begin
	case Message.LParam of
  	WM_LBUTTONDBLCLK: Show;
  end;
end;

const
  UWM_APPCALLBACK = WM_USER +  7 ;
  ...
  private
    procedure ShellIcon;
    procedure OnAppCallBack(var Message: TMessage); Message UWM_APPCALLBACK;

procedure TForm1.ShellIcon;
begin
with NotifyIconData do
  begin
    .....
    uCallbackMessage := UWM_APPCALLBACK;
    cbSize := SizeOf(NotifyIconData);
  end;
end;