To check if hardware is working and connected, use the PING command. Find out the IP address for each computer then open a command prompt window and type the command PING 192.168.0.1 (replace the numbers with the IP address of the computer you are trying to reach). Repeat on each computer. You should receive a message saying reply from 192.168.0.1. If not, there is a problem with the connection.
You need ICS enabled on one of the computers.
Disable firewalls while checking network connections. Once they are working then enable firewalls again.
You need at least one directory shared for a computer to be visable on the network.