help me figure out network thing

There are four computers in the house: my pc (running win7), living room pc (running XP), one roomie’s pc (running XP), and other roomie’s laptop (running linux, I think.)

My pc and living room pc are plugged physically into a router. Roomie’s pc and other roomie’s laptop connect to the router wirelessly.

My pc and the laptop are not involved in what I want to do. The living room pc has a bunch of movies that roomie wants to watch in his room on his pc. So I want to network living room pc and roomie’s pc so they can share files, excluding the other two computers.

As I said, one pc is physically plugged into the router, and the other connects wirelessly to the router. They are both running XP. I followed the instructions in windows for doing this (on both pcs), but no joy. Is there some problem with the way the computers are connected that prevents them from connecting together?

Also, if these two are connected into a workgroup with a separate name (“workgroup”), will that supercede or interfere with the shared internet connection (also a network) that the two wireless computers are using to connect to the internet through the router? If not, can the one roomie’s pc be connected to the workgroup and the router’s wireless network at the same time? (or will we have to combine them?)

Did you share the drive or folder that has the movies, xp would have a hand underneath the drive.

Both devices are on the same network , and both have the correct time/ time zone ?

Can either of the two devices see each other, if so then its a permissions issue.

Declan