Автор: http://www.swissdelphicenter.ch

{....}

   private
     procedure WMNCHitTest(var Message: TWMNCHitTest); message WM_NCHITTEST;

      {....}

 procedure TForm1.WMNCHitTest(var Message: TWMNCHitTest);
 begin
   inherited;

   with Message do
   begin
     if Result = HTCAPTION then
       Result := HTNOWHERE;
   end;
 end;