I would suggest running the "set up a home or small office network" wizard to be found in the left hand-bar of the network connections section of the control panel. Alternatively click on start --> All programs --> Accessories --> Communications --> Network setup wizard.
Both paths lead you to the same wizard - should be self-explanatory
once you run it on each machine. A reboot may be in order after you run them to allow the IP addresses to sort themselves out.
HTH
