Can't connect to Interner using ethernet to Vista

I originally connected my Dell tower to another PC by WIFI. But the connection was intermittent due to the distance between the PCs and walls between. I then purchased and installed a Netgear adapter that uses house wiring as the ethernet connection. All components are properly installed and the light in the back of the Vista is on but despite trying different settings, I can't get it to connect. What do I need to do?