Look, I apologize, but that was the 3rd time it'd happened. I've been fighting this for days now, and I've gotten no closer to a solution than I was when I started. I mentioned early on that I was close to tossing it away - that gives you an indication of how frustrated I've been. I've been told to remove my video card and boot into safe mofe (if I have no video card I have no display), been told to install a BIOS update from normal mode when I'd already clearly specified that after the NIC driver update I could only boot in safe mode, then I was scolded for 'pulling the plug' then scolded for interrupting chkdsk.
Anyway, apologies all around. And please accept them since it's only my exasperation that has brought out some uncharacteristic rudeness in me.
I do have some news....
I booted normally, uninstalled the ethernet driver in device manager, and reinstalled it from the flash drive. Partway through the InstallShield Wizard I get a msg box:
The Realtek Network Controller was not found. If Deep Sleep Mode is enabled Please Plug the Cable.
That is exactly how it read, including the strange capital letters. I, once again, have no clue what it means. If anyone's still willing to jump into the fray, I'd be humbled for the help.