请教大侠，TOpendialog编译错误，请指教？

小弟初学delphi，做一个多媒体播放器，用的是delphi7.0.有下面问题，请大侠指教，感激不尽。unit palyer1;interfaceuses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, Buttons, StdCtrls, OleCtnrs, MPlayer, ToolWin, ComCtrls,
  ExtCtrls;
type
  TForm1 = class(TForm)
    CoolBar1: TCoolBar;
    CoolBar2: TCoolBar;
    Label1: TLabel;
    MediaPlayer1: TMediaPlayer;
    OleContainer1: TOleContainer;
    RadioButton1: TRadioButton;
    RadioButton2: TRadioButton;
    RadioButton3: TRadioButton;
    RadioButton4: TRadioButton;
    RadioButton5: TRadioButton;
    RadioButton6: TRadioButton;
    Opendialog1: TOpendialog;//若不删除，编译时IDE就说得输出它；
                             //若删除它，就在下面产生错误
    Label2: TLabel;
    SpeedButton1: TSpeedButton;
    SpeedButton2: TSpeedButton;
    procedure Label2Click(Sender: TObject);
    procedure FormCreate(Sender: TObject);
    procedure SpeedButton1Click(Sender: TObject);
    procedure RadioButton1Click(Sender: TObject);
    procedure RadioButton2Click(Sender: TObject);
    procedure RadioButton3Click(Sender: TObject);
    procedure RadioButton4Click(Sender: TObject);
    procedure RadioButton5Click(Sender: TObject);
    procedure RadioButton6Click(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;var
  Form1: TForm1;implementation{$R *.dfm}
procedure TForm1.SpeedButton1Click(Sender: TObject);
begin
opendialog1.execute;\\若上边删除，这里就说opendialog没有声明。if MEDIAPLAYER1.FileName<>' ' then
MEDIAPLAYER1.FileName:=opendialog1.filename;
if(RadioButton1.Checked=flase) and (RadioButton2.Checked=false) and
(RadioButton3.Checked=flase) and (RadioButton4.Checked=flase) and
(RadioButton5.Checked=flase) and (RadioButton6.Checked=flase) then
MEDIAPLAYER1.DeviceType:=dtautoselect;
MEDIAPLAYER1.Open;
end;procedure TForm1.RadioButton1Click(Sender: TObject);
begin
MediaPlayer1.devicetype:=dtAutoSelect;
end;procedure TForm1.RadioButton2Click(Sender: TObject);
begin
MediaPlayer1.devicetype:=dtAutoSelect;
end;procedure TForm1.RadioButton3Click(Sender: TObject);
begin
MediaPlayer1.devicetype:=dtAutoSelect;
end;procedure TForm1.RadioButton4Click(Sender: TObject);
begin
MediaPlayer1.devicetype:=dtAutoSelect;
end;procedure TForm1.RadioButton5Click(Sender: TObject);
begin
MediaPlayer1.devicetype:=dtAutoSelect;
end;procedure TForm1.RadioButton6Click(Sender: TObject);
begin
MediaPlayer1.devicetype:=dtAutoSelect;
end;end.