Is there a way to change video files to music files?

I have dish network and with it comes Surious Satalite radio. I have windows media center with a tv tuner card which enables me to record tv. I can record the music files on a cd but the video files are to large and cant get much music on them. Is there a way to compress those files so they fit on a standard audio cd so I can play them in my car. Thanks in advance. Doug