a) his router is at one end of his house
b) his Xbox and PC are in the same room at the other end of the house
c) he wants to be able to hook his PC and Xbox up to the same network, preferrably without using wireless
He may not have a crawl space under his house (please confirm OP), so running cable may not be the easiest of options.
A couple of posters suggested running a cable between the PC and Xbox in the same room. But will this work? (I don't know myself).
I've been using EoP for the past few months in an apartment block, and it seems to work sufficiently for me 98% of the time. The main strain on my network is delivering HD content from my HTPC downstairs to an XBox 360 extender in an upstairs bedroom. As Cyril is well aware in my case, wireless just didn't cut it for me.
And finally, falling into the Power over Ethernet trap (as opposed to Ethernet over Power) must be more common than I thought. I confused the hell out of Cyril and Rustygonad many times by getting the order of these two words around the wrong way!
I hope my post adds something to this discussion...