If you are connecting two computers up with an Ntl Cable modem you'll need:
In the main computer : two nic's (or one nic for the network and a USB port for the modem, many recommend two nics though) about £10 each
In the client computer: one nic
Start with the main computer, I'm assuming its like the XP wizard, run the network setup wizard and then at the end tick the "create wizard disk" which then allows you to take the wizard and your settings to the next computer. Run the disk on the next pc and you should be away
I hope thats all right, I'm still not all that good at networks.