I think you are out of luck there. I bought a USB (not HD)about a year ago hoping to get it to work on my Linux box. I never did find a driver for mine which of course is the first thing you need: http://www.linux-usb.org/ or here: http://www.mythtv.org/wiki/index.php/Video_capture_card - very limited at best. If your card is among the lucky few then you might have a chance though horse power of the NIT will be the next major problem. If the card contains all the mpg decoders in hardware then just maybe....
It would be cool I must admit.

C