Оформил: DeeCo
Автор: http://www.swissdelphicenter.ch

var
   tutup: Boolean;
   i: Integer;

 procedure TForm1.Timer1Timer(Sender: TObject);
 var
   reg1, reg2: hrgn;
 begin
   if tutup = True then
   begin
     i := i + 10;
     reg1 := CreateRoundRectRgn(0 + i, 0 + i, Width - i, Height - i, 20, 20);
     SetWindowRgn(Handle, reg1, True);
   end;

   if i >= Width then
   begin
     tutup := False;
     i := 1;
   end;

   if tutup = False then
   begin
     i := i + 10;
     reg1 := CreateRectRgn(0, 0, (Width div 2) - i, Height);
     reg2 := CreateRectRgn((Width div 2) + i, 0, Width, Height);
     CombineRgn(reg1, reg1, reg2, rgn_or);
     SetWindowRgn(Handle, reg1, True);
     if i >= Width div 2 then
     begin
       tutup := True;
       i := 1;
     end;
   end;
 end;

 procedure TForm1.FormCloseQuery(Sender: TObject; var CanClose: Boolean);
 var
   reg1: hrgn;
 begin
   i := 1;
   timer1.Enabled := True;
   if MessageDlg('Exit now ?',
     mtConfirmation, [mbYes, mbNo], 0) = mrYes then
     CanClose := True
   else
   begin
     CanClose := False;
     timer1.Enabled := False;
     reg1 := CreateRoundRectRgn(0, 0, Width, Height, 0, 0);
     SetWindowRgn(Handle, reg1, True);
   end;
 end;

 procedure TForm1.FormCreate(Sender: TObject);
 begin
   tutup := True;
   timer1.Enabled := False;
 end;