Yes, Media Center can act as a DVR for any device/ cable system. However, you will need a dedicated STB for the media center to act as a tuner. Without a STB, you will only be able to record channels under channel 50.

There is talk of media centers with cable card capability. If that ever materializes, then you will be able to get a cable card and use the mediacenter directly connected to the coax and get all channels.