About bridging wireless cards, my understanding is as follows. The HomePNA card, once you find a driver for it, is just another wired card. Wireless cards on the other hand are fundamentally different from wired cards, because they have parameters like channel number and encryption that wired cards don't have. So if everything is packed into one interface then a bridge that handles wired cards won't be able to deal with wireless cards. That does seem to me like the wrong way to go about it, but I can't change Windows.

I guess this question is closed: Knoppix doesn't support the HomePNA card, but there may be workarounds that work in Knoppix and there may be other Linux distributions that do support the card. Thanks for helping me get to that point .