What IP addresses and subnet masks do your computers have?

Does your home network have a broadband router or other Internet
sharing device?  If so, it should have a built-in DHCP server that
assigns IP addresses to the computers.

If there's no DHCP server on the network, the computers will assign
themselves addresses in the same 169.254.x.x/255.255.0.0 subnet, and
they should be able to communicate with each other.

You can assign them static IP addresses, which will make the computers
start up faster:

1. Open the Network Connections folder.
2. Right-click the local area network connection.
3. Click Properties.
4. Click "Internet Protocol (TCP/IP)".
5. Click Properties.
6. Click "Use the following IP address" and fill in the values.

Use addresses from the ranges reserved for private networks by the
Internet Assigned Numbers Authority:

  10.0.0.0 - 10.255.255.255
  172.16.0.0 - 172.31.255.255
  192.168.0.0 - 192.168.255.255

Examples of pairs of private network addresses are:

10.0.0.1 and 10.0.0.2, subnet mask 255.0.0.0
172.16.0.1 and 172.16.0.2, subnet mask 255.240.0.0
192.168.0.1 and 192.168.0.2, subnet mask 255.255.255.0