Lets say you have to connect one more computer to the main computer which will share his internet connection. One computer need two network adapters. Through one LAN card will flow internet traffic from the service provider and through the other LAN card will flow internet traffic to the other computer.
Under Windows XP you have to follow this steps:
1. From Start -> Settings -> Control Panel -> Network Connections in the list with connections you have to see two ore more connections (one connection for each LAN card).
2. Right click on the connection to your Internet Service Provider and select Properties.
3. Next select Advanced Tab and check "
Allow other network users to connect through this computer's Internet connection" checkbox.
4. Now will appear one more checkbox. You can check it if you want other computer from your network to manage the shared connection. By default this option is disabled.
5. Click OK button and close Properties window on this connection.
6. Now go to second connection and have to do all of this again. Also in
Properties in TCP/IP protocol click on Configure button.
New window with several fields will appear.
IP Address: 192.168.0.1
Subnet Mask: 255.255.255.0
Default Gateway: leave empty
DNS Servers: leave empty
Next click OK -> Close and we are done with server configuration.
Next go to other copmputer (to which you want to share internet connection) and select Properties on his connection. Now set the following settings:
IP Address: 192.168.0.2
Subnet Mask: 255.255.255.0
Default Gateway: 192.168.0.1
DNS Server: 192.168.0.1
Next click OK > Close. Restart the both computers and everything have to be done. Now both of your computers have to share one internet connection.