Problem Networking XP and Vista?

I'm trying to network 2 computers, one using XP (Pro), the other using Vista. They are connected via a single ethernet cable. They do not detect each other, and attempts at pinging have failed. It does detect the wire however, the computers just can't "identify" one another. I have edited the TCP properties for IP addresses, and enabled sharing. I have attempted this connection with firewalls on and off. The workgroup names are the same as well, so that is not the issue either. There is no readily apparent hardware issue, as mentioned earlier the wire connection itself is detected and the lights in the back of the PC's are green. The network wizard has failed to work as well. I can't even share files, however it is worth noting that one computer accesses the internet via a wireless adapter (the XP), while the other (Vista set-up) has no means of internet connection, besides the hopes of networking the two to operate off of the one adapter in the XP. I don't know if that is even possible, but at the moment I would just like to be able to share files. Any suggestions to fix this problem would be appreciated!