Honestly, I’m not sure.
I actually went on Machinima’s forums earlier today, and it seems like capture cards do work with PCs, since people have several posts that imply that they have video captured using capture cards.
I need to finish a paper at the moment, but, if I find out something interesting, a hardware alternative to Fraps would certainly be interesting, since even Fraps can take a toll on framerate on weaker systems when recording.