First you will need to install 2 network cards on your computer (the server)
- One card which receives "internet" from your ISP(internet service provider)
- Another that sends "internet" to your friends
- You will create a Local Area Connection from Control Panel like this:
1. Network Connections
2. Create New Connection, configured with the IP information provided by your ISP (Ip Adress, Network Mask, Gateway, DNS 1/2)
The second card (and another Local area connection 2 that sends internet to your friends) with:
1. IP address: a local Ip adress (Ex : 192.168.1.1)
2. Network mask: 255.255.255.0
3. Gateway: you can leave it blank

Your friend/s will create a Local Area Connection configured like this :
1. Ip address: 192.168.1.xx
2. Network Mask: 255.255.255.0
3. Gateway: The Ip adress of the second card on the server
4. DNS 1/2 only if required.

On the second connection that you created you will activate from :
1. Control Panel
2. Network Connections
3. Local area connection 2
4. Advanced, check the box: "Allow Other Users to connect through this computers internet connection".

Now, the connection will be made with UTP/STP/FTP cable from server (from the second network card) to a Switch and from there cables to your friends Computers (they will need network cards as well) .

NOTE: the configuration was though WITH DHCP mode enabled from windows sharing or with ROUTER.