I just went through this same situation and downloaded every driver I could find until suddenly it hit me: Is the Device Enabled in the BIOS?
Sure enough, both the on-board NIC and WLAN were "disabled". I couldn't believe it. Enabled and bingo. Networking back.
I should have known better when neither device even showed up in Device Manager. But, as we often do, we don't look at the obvious first. Hope this helps someone.