If its a router, they could possibly be blocking some of the traffic. If they are on seperate subnets or networks, then that may be the reason you don't see them in windoze (but I'm not a windoze networking dude). Did you try to conenct via the IP addr?
Now when you say:
My buds and I would like to play some Counter-Strike/Halo over a LAN. The problem is this, we cannot see each other in the game lists, nor can we share files/folders.
What do you mean? The 'game list' you refer to in Counter Strike is hooked thru Steam so it shouldn't matter. If one of you is running a CS server you simply connect to the server via the IP addr.