You can look into this guy. He's why I know how tedious custom AMD drivers are as he releases them for Macs Apple and AMD no longer wish to support.So, it would be very much appreciated if someone could and wanted to contribute with a deeper and more detailed knowledge on how to mod for example latest Adrenalin 2020 Win 7 drivers to work for Win 8.1!! If it is possible at all...??
His drivers require some tinkering in Safe Mode, like using the community GPU driver uninstaller to fully remove any drivers. OP's PC might have failed to boot because of a conflict caused by the drivers not being fully uninstalled. I can't say for certain, though, but this site should be a good starting point.
All this said, I'm still of the mind that moving to Linux is a better solution. AMD systems are thriving on it right now, and it's really beginning to make Windows look obsolete what with the advancements there and in WINE. WINE 6 just hit stable, and it's brought soooo much to the table.