I'll jump to the bottom here - XP Pro will work with networks, but I don't know how to set it up between the two operating systems. I have two computers running Win7 Ultimate and it was surprisingly easy to set up a network so I can see what is on both computers from either one. I set it up on my main computer than set it up on the older one, and there it was ready to go, but I had to go back to the first computer to approve it. They see each other through the router because they're both wired. I suppose it would be similar if they were wireless.

SRS