You'll need some kind of TV tuner card (preferrably with hardware encoding, so that your CPU doesn't get bogged down) like a Hauppauge PVR-150/250/350/500, etc, and a large hard drive. Many tuner cards' default recording format is MPEG-2, and depending on the picture quality you choose to record in, a 1-hour program can easily eat 3GB of drive space.
I can't speak on the DVR choice, since I don't have any experience with one.