Go to your device manager.
Hold down windows key (between ctrl and alt, the windows logo) and hit the "r" key. This opens a run box. In the blank space type:
devmgmt.msc
Hit enter. With your device manager open, you should have an Ethernet controller or adapter with a yellow triangle next to it. Double click this, go to your details tab and on the drop down menu select hardware ids. You will have ven_XXXX&dev_XXXX. Go to pcidatabase.com on a computer or device with internet access. Enter the 4 characters of your vendor ID in the search vendors bar on the top. If your vendor ID is 8086, it is definitely intel. Once you know who your vendor is, take your device ID and search on the same website at the top where it says to search devices. Once you know what network adapter you have exactly, you should be able to go to the manufacturers website and download a driver. Just beware, if you shy away and start searching other sites you might end up downloading some adware instead of a driver.