Well, that's really two different things.

I'd take a look at the docs for the adpater and see how it says to put it in ad-hoc mode. (For that matter, how does it know what network to join?) Anyway, what I'm getting at is that you might be able to install it on a "normal" computer, set it to ad-hoc mode, then plug it back into the TiVo. I have no idea that that will actually work, but it's a possibility.