If you have previously enabled Internet Connection Sharing (ICS), and you decide to use a router instead of ICS to share an Internet connection among two or more computers, you'll need to disable ICS.
Open Network Connections by clicking the Start button , clicking Control Panel, clicking Network and Internet, clicking Network and Sharing Center, and then clicking Manage network connections.
Right-click the shared connection, and then click Properties.
If you are prompted for an administrator password or confirmation, type the password or provide confirmation.
Click the Sharing tab, clear the Allow other network users to connect through this computer's Internet connection check box, and then click OK.