ICS or Internet Connection Sharing is a tool used in Windows to share your internet conection be it Wifi or Lan.   To set up the conection you will need the following:

Ethernet Cord
Laptop or Desktop running Windows 7
Administrative Rights on that computer

Now for the steps.

1. Open Network and Sharing center
           To do this open your start menu and search Network and Sharing
2. Click Wireless Network Connection (Your Router Name Here)
3. When the dialog box opens click Properties
4. Then in the sub-menu click the tab Sharing
5. Check the box that says (Allow other Network users to connect to this computer's Internet connection.
6. Press OK and close all open windows.
7. If you are using a laptop make sure it is plugged in then plug the Ethernet cable into the slot on you computer.
8. Turn the other computer on and there you go.

Note- This also allows you to connect your Xbox 360 or any other device with an Ethernet Connection slot to the Internet.   Also please make sure you disable your Windows Firewall I always seem to have a connection problem when it is enabled because it tries to block the other devices.
 
First make sure you are connected to the router 

Then open Start Menu and click Network Conections 
If you are connected to the router threw Wi-Fi them double click Wireless Network Connection

Third click the Support tab in the Wi-Fi connection window

Copy the Default Gateway Example-192.162.0.1

Paste it into your internet window make sure you put http:// 

Example- http://192.162.0.1


 
 
Wi-Fi Networks

Internet Sharing-

ICS or internet connection sharing is a feature given is most operating systems the most current is Microsoft Windows 7.   This feature allows you to share both internet and files by having one computer connected to you Wi-Fi or Wireless router threw a LAN or Ethernet cable, then of course have a(n) ad hoc network setup so that all of the computers you wish to share internet with can connect to it.  

Notes-

Security is a big problem in our world so it is very important that when you setup your ad hoc network that you enable security no matter what OS you use Windows XP Vista or 7 and when it comes out Windows 8

In addition, it is very hard to set this kind of connection up with a(n) computer using Windows XP I personally recommend only trying the setup with a Windows Vista or 7 OS because they are both much easier.

To prevent Copyright Infringement

I do not own Microsoft or Windows!! 

Here is a document that will show you how to set up ad hoc networks on Windows XP 
Click here to download