Windows Doesn't Recognize Ethernet

I ran Windows 8.1 on my desktop machine a few months ago, and later upgraded to Windows 10. Everything worked great at that time, but since have replaced Windows with Linux. Now I'm trying to install Windows again, with the same 8.1 disk that I used for my earlier installation, and my ethernet connection isn't found. (this is a direct wired ethernet, not wireless) I've installed with a local user account, dug into every networking utility in Windows, but whatever I do the internet goes undetected. I've run the ethernet thru different routers, and even circumvented the router all-together, but no luck. Has my 8.1 disk "expired"? Any thoughts on what's happening here?

JohnC said:

Hi YourPalMark, welcome to Ten Forums. Your 8.1 disk has not expired. If you were activated before, you still are. Try either updating the drivers for the network adapter or resetting your network adapter first. Troubleshoot network adapter problems
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Edit. The other thing to try is unplug the ethernet cable, reboot the router/modem, plug it back in and try to set up a new connection.

I've tried all that without success. The only thing that I didn't try was to enter the IP info manually. (wasn't sure how to do it, particularly on a system with no internet)
I just saw your edit with the added remark about rebooting the router and modem, something I didn't do. Should I install Windows with a local account, and then try the router/modem reboot?

Got it going John, and I really appreciate your getting me thinking. (no small feat!) It turns out it was the driver for the network adapter after all, and a visit to the Realtek website fixed me up. Thanks!