The way I do it is with an ethernet hub. I plug the cable on both PC's and the modem into the hub. The only tricky part is the the cable that now connects your modem to the PC is likely a special crossover cable, and it has to be replaced with a standard cable. I believe most hubs have a special port which is intended to daisy chain another hub. If you use that port on the hub then you may get away with using the special crossover cable on that particular port. I have done it that way.