uses 

  registry; 

function IE_installed(var Version: string): Boolean; 

var 

  Reg: TRegistry; 

begin 

  Reg := TRegistry.Create; 

  with Reg do 

  begin 

    RootKey := HKEY_LOCAL_MACHINE; 

    OpenKey('Software\Microsoft\Internet Explorer', False); 

    if ValueExists('Version') then 

      Version := ReadString('Version') 

    else 

      Version := ''; 

    CloseKey; 

    Free; 

  end; 

  Result := Version <> ''; 

end; 

procedure TForm1.Button1Click(Sender: TObject); 

var 

  IE_Version: string; 

begin 

  if IE_Installed(IE_Version) then 

    ShowMessage(Format('Internet Explorer %s installed.', [IE_Version])); 

end;