como crear un cronometro completo

[[Delphius]]

¿estás seguro? Prueba con esto:

Código Delphi [-]
unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, ExtCtrls, StdCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    Timer1: TTimer;
    Button2: TButton;
    procedure Button1Click(Sender: TObject);
    procedure Timer1Timer(Sender: TObject);
    procedure Button2Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;

var
  Form1: TForm1;
  HoraInicial: TDateTime;
implementation

{$R *.dfm}

procedure TForm1.Button1Click(Sender: TObject);
begin
  HoraInicial := Now;
  Timer1.Enabled := true;
  Button2.Enabled := True;
  Button1.Enabled := False;
end;

procedure TForm1.Timer1Timer(Sender: TObject);
begin
  Form1.Caption := 'El cronometro cuenta : ' + TimeToStr(Now - HoraInicial);
end;

procedure TForm1.Button2Click(Sender: TObject);
begin
  Timer1.Enabled := False;
  Button1.Enabled := True;
  Button2.Enabled := True;
end;

end.

Debería funcionar. A me funciona apropiadamente.
Saludos,