如何在不同的系统(win98,win2000,win xp)下判断是否接入internet网?

procedure TForm1.Timer1Timer(Sender: TObject);var b: array[0..4] of Byte;begin with TRegistry.Create do  try  RootKey := HKEY_LOCAL_MACHINE;  OpenKey('System\CurrentControlSet\Services\RemoteAccess',False);  ReadBinaryData('Remote Connection',b,4);  finally  Free;  end; if b[0]=1 then Caption:='在线' else Caption:='离线';end;