| Hey there
Quick answer.
You have to enable Internet sharing on that connection.
Make sure your main PC connected to the modem has an ip address or 192.168.0.1. It normally changes automatically when you activate Internet sharing.
XP - You'll find the setting in Control Panel, Network Connections, (right click on the connection you use) select properties...
Vista - Control Panel, Network and Sharing Center, (Left Pane - click Manage Networked connections).. right click on the connection...
It is possible and have set it up for clients a few times.
Hope you succeed.
Cheers
Grant |