TRegistry 释放内存错误

procedure TForm1.Button1Click(Sender: TObject);
var
reg:TRegistry;
begin
reg:= reg.Create ;
reg.RootKey:=HKEY_CURRENT_USER ;
if reg.OpenKey('\Software',True) then
  reg.WriteString('222','111');
  reg.CloseKey ;
  reg.Free;  //这里为什么会出错
end;

end.