Technogeek question -- TV tuner

I had to pop for a new laptop a few weeks ago and got one with Windows 7, then saw the ad about how to use the computer as a DVR.

In looking through the Media Center program, I learned that I need an external TV tuner (plug one end into a USB port, screw the cable onto the other end).

The question is: What kind of tuner should I get? Brand names, price ranges, CPU requirements, etc.

I don't record much, but it would be nice to get a few things I want to watch. Apparently, my desktop (Vista) has similar software, so I could plug it in and save the laptop for work (desktop is in a different room from TV, but a cable splitter and about 50 feet of coaxial fixes that).

Neither computer has much on it except for what it came with (and a good chunk of that has been removed), so memory capacity shouldn't be an issue for now. I can always get an external hard drive to save things to if I want to keep them for repeated viewings.

If anyone who has a setup like this has advice, I thank you in advance.