The only thing I can say is look for a USB 2.0 card (since that's almost as fast as FireWire and fast data transfer for video is the key to good caps).
Go to CompUSA and buy several of the USB 2.0 cards from companies like Aver, Pinnacle etc... and see which one works best.
The reason why I say CompUSA is because you can return all the ones you didn't like for a FULL REFUND even though you used them.
BTW, if you ever get a card for your PC may I recommend this one:
http://www.digitalconnection.com/produc ... usion5.asp
Makes great HD caps and a relatively low price.