It sucks that you have to preemptively apologize to the angry gods of the forum.
Anyhow, you need a tv tuner card. Hauppauge is the de factor standard for those, the pvr 150 is their best single tuner card, and they make a double tuner card (can record two streams simultaneously). For your software, SageTV and BeyondTV are the heavyweights for aftermarket Tivo software. Generally the software included with tuners is lame. You could also use WindowsXP media center edition for your software instead, but its a bit more expensive.