From the sound of it Si already has an ethernet card in his PC but can't get a connection using it.
It could be that the ethernet adaptor in his PC is not enabled in the bios or that the ethernet drivers haven't been loaded. Make sure the RJ45 lead is straight through and not crossover.
Si, Have a look in Device Manager first to see if there is an ethernet card listed under Network Adapters and if it is working correctly. If it is then have a look at the CDs and disks you got with your PC for an ethernet driver and install it.
Robin Walker haas an excellent site for troubleshooting connection problems at
http://homepage.ntlworld.com/robin.d.../ethernet.html which you can have a look through if at any time nobody is around to help.