A common question is "How can I share my broadband connection with 2 or more PC's?".

There are several ways which this can be achieved and I will try and explain the basics of each method.
Each method will need a Network Card (NIC) to be installed on each PC. Most new PC's come pre-installed with a Network Card, but if you don't have one you can buy these from about £8. You can even buy USB network adapters so that you don't have to open up the PC.


Simple connection of 2 PC's.

If you only have 2 PC's on your network the cheapest way of doing this is to use a special type of network cable between the 2 PC's. However it is very important that you use what is known as "crossover cable" since normal network "patch" cable will not work using this method.

If you are having problems purchasing a long length of cross over cable it is possible to use a short length of crossover cable joined to normal patch cable using a network connector/coupler.

When setting up ICS, The machine that is connected to the adsl usb modem needs to be a dedicated "gateway PC", and must be switched on and connected before the other machine can connect to the internet.

You will need to install and set up Internet Connection Sharing (ICS) on your network.
ICS is supported by Windows 98SE and newer.
More information on ICS can be found at Microsoft ICS set up and there's also a good guide at Annoyances.org 

Simple connection of 2 or more PC's using an existing usb modem.

Rather than use crossover cable you can purchase a network switch or hub to network all your PC's together.
A network switch can be purchased from somewhere like Scan for about £10. Most hubs/switches have at least 4 ports for connecting PC's plus one uplink port which my be connected to a router.
When using this method a gateway PC has to be switched on and connected before any other PC's on the network will be able to access the internet. Using this method requires you set up ICS.

More information on ICS can be found at Microsoft ICS set up and there's also a good guide at Annoyances.org 

Networked (Ethernet) Connection using an adsl modem/router.

The best solution is to purchase a combined adsl/modem/router. A router is in effect like a small PC which has its own processing power and its job is to control the traffic to and from your adsl connection before it reaches your PC's.
Most routers have their own inbuilt firewall, and with the addition of NAT, will make your network a lot safer environment and less likely to suffer from external attacks.
This type of connection can truly stay up 24/7 and is not dependant upon any of the PCs on the network. One port routers may be used in conjunction with a network switch to connect several PCs.

Alternatively 4 port routers can connect up to 4 PC's without the need for a separate network switch or hub

Wireless Networking.

Finally the most advanced method is wireless networking which allows you to be able to connect to the internet without the need for network cables. You will need to purchase a combined adsl modem/router/wireless access point.
Each device that is attached to the wireless network will need a special Wireless adapter. PC's can have either a PCI adapter, or you can purchase USB ones to save opening up the case. Laptops require a PCMCIA card.
Some wireless routers require a cabled connection for first time set-up although the more newer routers will allow wireless configuration. Make sure that you secure your wireless network to stop other users such as your neighbours being able to access your network connection.

A selection of routers can be reviewed at adsl guide.
There is a good guide on setting up gaming networks on the BT site here.