Hello everyone, can you help?

installed sky bb on girlfriends laptop with no problems, using ethernet cable, everything fine. Tried to install on my old pc using usb/ethernet adapter with no joy. before i start getting into really technical stuff, am i missing something obvious? we don't want to share files or have a wireless network, just occasionally want to surf at the same time using cables. i seem to be going round in circles getting more and more confused, show me the way....