a Clean install of 8.1, if you could find a disk you might do a repair install. Roll back to a date before you ran the upgrade to 8.1, with one of those back up Images you have been keeping up with?
G752VY-DH72 Win 10 Pro
512 GB M.2 Samsung 960 Pro
1 TB Samsung 850 pro 2.5 format
980m GTX 4 GB
32GB DDR 4 Standard RAM
Z97 PRO WiFi I7 4790K
Windows 10 Pro
Z97 -A
Windows 10 Pro