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.
Start IE web browser. Select-Tools-Internet Options-Connection Tab
In the “Connection” screen, there are three selections:
“Never dial a connection”,
“Dial whenever a network connection is not present”
“Always dial my default connection”.
If you can make a selection, select “Never dial a connection”.
If you cannot make a selection, select “LAN Settings”
Untick marks next to any of the displayed Options:
“Automatically detect settings”,
“Use automatic configuration script”
“Use a proxy server”.
Click “OK”. Then click “OK” again in the “Internet Options” page
Network Adapter Setup
Also called a LAN card (Local Area Network) or NIC card (Network Interface Connection)
Double-click on the “Network Connection”
Left-click on the “Local Area Connection” associated with your network adapter
Select “Properties” from the drop-down menu.
In the “Local Area Connection Properties” window all boxes should be ticked
At bottom of display tick the box “Show Icon in Notification Area When Connected
A display Icon will appear in the task bar when you have finish the setup
Click-Internet Protocol (TCP/IP) Click the “Properties” button
Select “Obtain an IP address automatically
Select “Obtain DNS server address automatically”
Click- Advanced-Click-WINS Tab-Tick-Enable LMHOSTS Lookup if untick
Do Not Change Any Other Setting
Your computer network card is now configured for use with the Modem/Router