Sharing one Internet connection among all of the computers on your home network saves time because you only have to set up one connection. And it saves money, because you don’t have to buy an individual Internet account for each computer.
There are two ways to set up Internet connection sharing: by using a router, or by using Internet Connection Sharing (ICS).
Using a router
How it works: Each computer connects to a router (sometimes called an Internet gateway device). The router, which can be wired or wireless, connects to a broadband (DSL or cable) modem, and the modem connects to the Internet.
Make sure your router has a built-in firewall. A firewall can help stop unwanted connections to your network from the Internet.
How it works: One computer on the network is designated as the host computer. The host computer connects to the Internet and the other network computers share that Internet connection.
This method is a bit less convenient because it requires the host computer to be left on all the time. However, it is the best method if you have a dial-up Internet connection, or if you use a modem with a USB connection.
How to configure ICS from MS Windows 7 (Youtube Video)