If any firewalls are installed on any of the PCs, uninstall them.
This includes Zone Alarm, Sygate, Kerio, Norton Internet Security, Zero Knowledge Freedom, Cisco VPN Client, F-Secure, McAfee Firewall, Trend Micro, Comodo, PC Tools Firewall Plus etc.
In many cases, disabling the firewall is not enough; you have to actually uninstall it.
Do not install or re-install the firewall until after you have the network functioning properly.
You only run the CD if connecting to modem using a USB port
Check the manual and configure the modem/router via your browser
Once you have access the modem/router use the wizard to set up system