Perhaps any or all of these observations may help you:
* I have a Win 7 laptop with an internet/networking option which I can choose during setup, 'Allow other computers to access the internet through this computer.'
* I have an internet gateway which can connect via wifi or ethernet to my computers. (Normally I connect them to the ethernet ports.) If I want to do something else with the ethernet, or if the ethernet does not get recognized, then I turn on the wifi card. Then that works.
* Sometimes one computer can see the other simply by having both hooked up to the gateway, by wire or by wifi.