Do you know what lan card you have, whether it be intergrated or not? If so, google it for the right drivers.
If your computer was made by a manufacturer, say dell, goto dell.com and look up the drivers for your lan.
Tell it what your os is, then look under network or internet for your drivers.
Look for the most updated that is a driver, not application.
I can definatly help you, this is my area. Tell us more about your setup, as in; is it a custom or manufactured computer? If so, what model.
When you go to device manager do you have any yellow marks next to your lan internet or have anything that says unknown?