De o Windows 7 ajuda no Compartilhamento de Conexão com a Internet :
To enable ICS (Internet Connection Sharing), on your host computer:
Click to open Network Connections.
Right-click the connection that you want to share, and then click Properties. If you're prompted for an administrator password or confirmation, type the password or provide confirmation.
Click the Sharing tab, and then select the Allow other network users to connect through this computer’s Internet connection check box.
Notes
The Sharing tab won't be available if you have only one network connection.
You can choose whether to select the Allow other network users to control or disable the shared Internet connection check box.
Optionally, to allow other network users to use services running on your network, click Settings, and then select the services you want to allow.