I've seen a lot of motherboards and soundcards with S/PDIF input. My Creative Labs X-Fi Elite not only has S/PDIF input, but it will decode AC3 input, too.
If your computer has an ASIO driver for the audio then you can use File > Open Live > ASIO Line In to route the audio through JRiver.
The Tascam US-366 has ASIO drivers and S/PDIF input if you want to buy something external. However, using the CD player in the computer is a much better solution than trying to connect an external CD player.