TV tuner cards and external USB tuner devices give your Windows Media Center the same capability your TV has to tune to specific channels. If you have one tuner then you can watch or record one program at a time. If you have multiple tuners then you can watch a program at the same time that you record others up to the number of tuners you have.
In this article I'm going to explain why you'll want an Internet Home Theater System (iHTS). I'll show you how to use an old PC or select the right PC and other needed pieces to plug into your existing home theater system to end up with a wow-factor iHTS. This was a high-friction process for me. I want to provide the information you need to make it a low-friction process when you do it.