uses 
  {...,} OleCtrls, WMPLib_TLB;

procedure TForm1.FormCreate(Sender: TObject);
begin
   WindowsMediaPlayer1.URL := 'mms://live.rfn.ru/r24_hq';
   // Убираем стандартные кнопки проигрывателя
   WindowsMediaPlayer1.uiMode := 'none';
end;

// Воспроизведение
procedure TForm1.Button1Click(Sender: TObject);
begin
   WindowsMediaPlayer1.controls.play;
end;

// Пауза
procedure TForm1.Button2Click(Sender: TObject);
begin
   // Для потоков не работает
   WindowsMediaPlayer1.controls.pause;
end;

// Остановка
procedure TForm1.Button3Click(Sender: TObject);
begin
   WindowsMediaPlayer1.controls.stop;
end;

uses 
  {...,} OleCtrls, WMPLib_TLB;

procedure TForm1.Button1Click(Sender: TObject);
begin
   WindowsMediaPlayer1.settings.volume := 50;
end;

uses 
  {...,} OleCtrls, WMPLib_TLB;

procedure TForm1.Button1Click(Sender: TObject);
begin
   WindowsMediaPlayer1.enableContextMenu := False;
end;

uses 
  {...,} OleCtrls, WMPLib_TLB;

procedure TForm1.Button1Click(Sender: TObject);
begin
   WindowsMediaPlayer1.ControlInterface.stretchToFit := True;
end;

uses 
  {...,} OleCtrls, WMPLib_TLB;

procedure TForm1.Button1Click(Sender: TObject);
begin
   WindowsMediaPlayer1.settings.mute :=
      not WindowsMediaPlayer1.settings.mute;
end;

uses 
  {...,} OleCtrls, WMPLib_TLB;

procedure TForm1.FormCreate(Sender: TObject);
begin
   WindowsMediaPlayer1.settings.autoStart := True;
   WindowsMediaPlayer1.URL := 'c:\test.mp4';
end;

procedure TForm1.WindowsMediaPlayer1PlayStateChange(ASender: TObject;
  NewState: Integer);
begin
   // Нужно дождаться, когда файл станет проигрываться.
   if NewState = wmppsPlaying then
      WindowsMediaPlayer1.fullScreen := True;
end;

uses 
  {...,} OleCtrls, WMPLib_TLB;

procedure TForm1.Button1Click(Sender: TObject);
begin
   if ( WindowsMediaPlayer1.playState = wmppsPlaying ) or
      ( WindowsMediaPlayer1.playState = wmppsPaused ) then
      WindowsMediaPlayer1.fullScreen := True;
end;