Install 2 network interface cards in one PC, give one interface a fixed ip address for example 192.168.0.1 and a subnet mask of 255.255.255.0; then bridge the second interface with the first using the network connections menus of windows. (LAN traffic is routed between the interfaces). Then prepare the other two pc's network interface cards using 192.168.0.2 and 192.168.0.3 respectively and the subnet mask identical to that of the first pc. Prepare or have TWO crossover cables made up with a suitable length. The hardware book website shows exactly how the pin-outs should be arranged. Still, network switches are cheap and a better alternative and if you ask around somebody may even give you one for a small fee. Then you may also wish to study the 'route' command in windows to facilitate LAN traffic of ip packets. Whatever it is you are trying to accomplish, all the best.