Ubuntu Networking :: Networking Involving Multiple IP Address Types - 192 And 172?

I have one router, a linksys. It allows wireless and wired connections, as is normal. I have two XP machinesby wire to the router and three linux machines connected wirelessly. The XP machines both have IP addresses beginning with 192.168. while my three linux machines have IP addresses that all begin with 172. None of the machines is connected with a static IP address. All are automatic DHCP.I am told that the above scenario makes no sense. However, such is what I have so, I trust, the theory and the fact do not gel. I would not care except that I cannot see - using the nautilus network servers program, all of the XP computers with some of my linux boxes.