If you've ever wondered what the socket with a red glow inside was, this article on the Vista Team Blog will reveal all.

It is an optical audio connection called S/PDIF. The important thing about it is that it is a digital connection so there is no loss of quality; Windows works in a purely digital sense with audio until it is time to send it to an output. Inevitably some quality is lost, which doesn't make sense if the output device is also digital and has to convert it from audio to digital again.

I was caught out on my notebook because the ordinary headphone socket was doubled up as the S/PDIF. I saw the red light and thought that there wasn't a headphone socket. Silly me!