Just so long as you have to phone jacks and a modem in
each computer you shouldn't have a problem, just plug them
in and go. As long as you don't try to connect them at
the same time your good. If you want to connect at the
same time you'll have to make a network, but if you
already have to NIC's than you won't have to purchase
anything, but a crossover cable to do this. Although
setting up internet sharing can be a pain so check out
www.practicallynetworked.com to accomplish this easily.
But if you just want to connect one at a time ignore all
this, and plug em in and go.