Here's an experiment to run. Connect the two PCs with a standard LAN cable. Go to the first PC (the "server") and set it to have a static IPV4 IP address of 192.168.0.1. Set the subnet mask to 255.255.255.0. Create a folder share while you are at it. Reboot the PC. Now, go to the other PC (the "client") and set it to have a static IP address of 192.168.0.2. Set the subnet mask to 255.255.255.0. Set the DNS server IP address to be 192.168.0.1. Reboot the PC. Once rebooted, try to ping 192.168.0.1. If you can, then you are good to go. If you cannot, however, you may need a crossover cable/dongle.
Hope this helps,