how to go from S/PDIF to input on computer

You would probably be able to do what you need with a good sound card. What are you trying to do, though? Usually, its the other way around. Most of the time you use the PC because you have audio stored on a HD and use it as a transport to play on your audio system. If you are going to play an actual CD or DVD, I don't see the benefit of using a computer. (Don't take my comments the wrong way. I just find your question interesting. I'm not saying you are doing anything wrong.)

If you can't get help here, try computeraudiophile.com. For technical questions, its a great resource. For issues regarding sound quality, stick with Audiogon.

i want to use the digital out to cpu to transfer vinyl.:-)

A Meridian 562 maybe?

"i want to use the digital out to cpu to transfer vinyl.:-) "

Now it all makes sense. To answer your question, though, you need to give us a little more info. Are you transferring your vinyl to have more convenient access to your music so you can do things like put it on an ipod or to listen in the car, or are you doing it to get the best sound possible and play the music on a high end system? Knowing that will allow you to really focus in on what you need to do.