IP address conflicts

A couple of times when rebooting my netgear router I get this message: The system detected an address conflict for IP address 192.168.0.2 with the system having network hardware address192.168.0.2. I get this on my desktop machine running windows ME. When I do ipconfig, I do not have a default gateway. If I connect my cable modem directly into my desktop machine, the internet works fine. But not if I use the router. If I use my laptop with the router, it works fine. So I think it is something with my desktop machine. I think I turned on this home networking thing and I do not know how to undo it. Any help would be appreciated.