If connecting via USB, yep he'll need to load drivers for the USB adaptor ntl supply, and that will be on the ntl CD.
If connecting via ethernet, then the ntl CD shouldn't be needed, but if the network card isn't properly enabled, drivers will be needed from the card manufacturer - possibly supplied with the PC if the PC had the card originally, or on a CD supplied with the card. If you check in control panel > System > devices you will see if the network card is active, or showing as having a problem (big question mark).
Once all is plugged in switch off the modem and computer. give it a couple of minutes, switch on the modem, couple more minutes, switch on the PC. Now you should be able to launch the ntl internet registrations.
More info here:
http://www.cableforum.co.uk/board/article.php?a=13