Have you tried running the setup disk that came with the router?
If you dont have a disk try this starting with the computers turned off. Make sure they are set for automatic IP addresses using dhcp.
unplug power to the modem and router, hookup cable between the modem and the wan port on the router, hookup cable between the 2 pcs and the router using ports 1 and 2 on the router.
Plug in the power to the modem and wait for the modem to initialize and get connection. Should take about 30 seconds or so. Plug in power to the router and wait for it to initialize and connect up.
Turn on 1 pc. Once its booted goto Start > Run> and type cmd, press enter. In the window that opens up type: ipconfig /all
You should see the IP address in the range of 192.168.x.x . x should be 0 or one for the first x and any number between 2 and 254 for the second number. Subnet should be 255.255.255.0. Gateway should be 192.168.x.1 where x should match what your pc is at.
Try internet and see if it works. If it does, in the address bar type 192.168.x.1 to access the router. From here you can setup passwords and any other options you want.
If this doesnt work then report back what the ipconfig /all display is: ip, subnet and gateway.