in your windows control panel, go to hardware and sound, and open the device manager.
expand the network adapters hierarchy, Select your ethernet card, and click the tiny icon physically located under 'help' in the menu - it looks like a little computer, and should be the last one. It will say 'enable' or 'disable' in the hover bubble when you mouse over it. if it's disabled, enable it. if it's enabled, disable it then enable it again, and then click the little icon that looks like a computer tower with a green up arrow - to "update driver software" Wait a minute, then see if you have a connection to the internet.
Hope that works for you. (you MIGHT have to restart too)