a 1394 adapter is a 1394 adapter, regardless if you are plugging it into another PC or a camera.. if you loaded XP and want to make sure that the adapter works properly, plug in a firewire device and see? Make sure that the device has proper drivers first by finding them for XP and installing them. You don't need anything special, just the typical on board driver or specs stating that the ports will work with XP and Vista.
Sure. it could be the wire too but without making sure that you are dealing with an adapter thats working properly, troubleshooting the integrity of a cable is pointless. As for your network settings, i only suggested that because you stated that you read an error stating that it wasn't enabled. So, you plugging in a couple of addresses within properties for tcp/ip that isn't enabled on an adapter doesn't fit well either.
1) make sure the adapter supports xp
2) make sure that you have your typical settings loaded and enabled for the adapter (should look just like local area connection properties for the most part)
3) plug the cable between the two
4) run the network wizard on both machines
It's really easy actually...