Quick answer no you don't need it, unless you are using a USB adaptor.
Power off the STB & PC.
Plug your ethernet cable to the PC's network card and to the STB (use the x-over adaptor if the STB on the back says you need it (mostly the older Pace STBs)
Power on the STB, let it settle
Boot up the PC, let that settle.
Now attempt to browse to any website. The ntl server should intercept you and point you at a registration page. You'll need the account password and PID that ntl provided to you.
If you must use the USB adaptor, you simply need to run the drivers from the ntl CD, not everything else that rebrands your IE, etc.
edit Homelone got there first
