The protocol is important. IF you are running an IPX game, there are issues with IPX gaming in environments that have both XP/2000 machines and ME/98. This happened when we were playing Red Alert 2 using IPX.
I'm not at home, so I'm going on memory of what options are on the screens. On the 2000/XP machines, the network configuration had more than one device showing up, even though we only had one NIC and one IPX configuration in the OS. The game had defaulted to the first. Changing both 2000/XP machines to the second device allowed the game to work. The 98/ME machines only had one device appearing in the list.
I have no idea what causes the "phantom" device.