I actually haven't received any questions from Linux users as of yet, because most seem to link their machines on their own. That one I can answer, since it requires little NT usage. Using the account you created on the NT machine, attempt to log into the Windows NT domain when prompted. When reading through the article, just ignore the fact that the game is Quake 2, and follow all of the other instructions. Check out the article here.
Switches are essentially intelligent hubs.
They vary in speed, with fast ethernet and standard ethernet switches being the norm. Although more expensive than hubs, switches have their noticeable benefits, especially on large networks. Unlike a hub, a switch sends data directly to the computer it is intended for, instead of offering it to all machines. Obviously, this cuts down on network traffic. Transferring data over a fast ethernet hub between three computers is probably comparable to performing the same task with a fast ethernet switch.