TO OTHERS WHO MAY VIEW THIS THREAD. THIS IS NOT A BASIC HOOK-UP TO FOLLOW. THIS IS FOR THIS PARTICULAR SYSTEM ONLY.
Connect s-video (out from dvd) to dvd s-video in(on receiver)
Connect s-video (out from receiver) to s-video in (on tv)
Use the coaxial (audio) connection between your dvd and your receiver. You really need a new cable for this, but for now, try one side of that black cable if it has a standard RCA at the end.
Don't hook-up the red and white ones.
Keep the connections between the cable box & tv.
http://i27.photobucket.com/albums/c166/duke44jb/tvtocablebox.jpg
http://i27.photobucket.com/albums/c166/duke44jb/cableboxtotv.jpg
The optical needs to go from your cable box (optical out) to your receivers (optical in)
I made some changes, so read this again.
I did not recommend using HDMI because 1) You don't have the cable, and 2) I didn't see it on your receiver. HDMI carries the video signal, and the audio signal.
The optical and digital coax carry the complete 5.1 audio signal. The red and white coax connections only give you left and right. This is why you didn't have 5.1. You have to use the on screen menu of a dvd to select 5.1 after you insert a dvd. Be sure you do this before viewing your movie. Also, most of your Comcast programming is going to be left and right only. In this case, select (pro-logic) surround or (PL11) surround on your receiver for surround simulation.
Your receiver may have a selection for the digital inputs. It may give preference to one or the other. You need to read in your manual to see if it does. It may say on the back. If it happens to give preference to the optical, you need to be sure your cable box is off while viewing a dvd.
You will also be able to watch tv without your audio system on if you wish. You have made the audio connection between your tv and cable box already. The audio system will have to be on for the dvd.