I do not recommend USB video-capture cards but I have no experience to support this bias in the last 5 years. I'm sure they're now magnificent wonderful Do-Everything units - at least, that's their marketing hype.
For the internal cards, I consider the old Hauppage 1200-series ($60-ish) to have a great foundation - it's own MPG processor, and it's a single-input source for sole, dedicated processing. The 1600-series is an updated version, and has yielded several years of top quality video captures.
Then there are the newer Hauppage dual-channel cards (2200 series) which allows two input streams to be processed simultaneously. Their cost is also doubled.
If you can find an old ATI Theater Pro 500-to-650 with all the package parts included, it will have a 'hydra head' attachment to allow its single plug to connect to almost every video-input source available. Very nice, but these units have been out of production for a few years. A used one would not be a terrible option IF the attachments and the Base CD are included. The Base CD is required for some updates to be installed, by the way, yet the CD is only referred to during those update processes as "existing", too - only an ID file is read, but nothing else is used on it. Grrr...
There are non-Hauppage cards, but almost everything under $70 will not have a hardware MPG encoder chip - it will all be software. The debate on this quality continues - I'd expect, at some point, that the video-results will be the same.
If I had to get a TV-recording PC, I'd find some cheap, used one with 2Gb of RAM, XP and go with a $60 Hauppage 1200 series. The resulting quality will not be altered by the PC - it's only affected by the TV Capture Card. Now, processing the video - file conversions, etc - THOSE can be affected by the host PC.
That's why God invented networks and 2nd computers.