Ok, I did preface this whole thing by saying I had not researched it much, but talk about feeling stupid when I saw this in my wireless router settings:

Yeah, that's right. Just tell it not to be a router... and it won't! Geeeeez what a bonehead. So changed that, and assigned all my wireless devices 192.168.1.x addresses, and presto.

The XBOX now sees my desktop PC. Next trick? Figure out how to get Windows XP Media Center edition. Probably not going to happen for a longgggggggg time.

Ahhhhhhh one network. All my machines and devices can talk to each other. I can transfer shows from tivo box to tivo box now too... cool.