Delphi XE

procedure TForm1.btn2Click(Sender: TObject);
var
  G: TGUID;
  S: string;
  bs: TBytes;
begin
  G := G.NewGuid;
  S := G.ToString;       //{9B60BA3F-8EE5-448F-BC9B-64FD98685ADB}
  mmo1.Lines.Add(S);
  bs := G.ToByteArray;
end;