It is a boot error, thats why you get it every startup -
https://neosmart.net/wiki/0xc000000e_selected_entry_could_not_be_loaded/
Do you know your product key for win 8.1?
You could try to clean install win 10 and use the 8.1 key as the license. That should get you past that error message at least.
On another PC, download the
Windows 10 media creation tool and use it to make a win 10 installer on USB
Anything on C drive you want to rescue? I think the menus are the same in win 8.1 as they are in 10
boot from installer
on screen after languages, choose repair this pc, not install.
choose troubleshoot
choose advanced
choose command prompt
type
notepad and press enter
in notepad, select file>open
Use file explorer to copy any files you need to save to USB or hdd
Clean install win 10 - follow this guide:
https://forums.tomshardware.com/faq/how-to-do-a-clean-installation-of-windows-10.3170366/
If your licence key doesn't work, you can click I don't have a key and win 10 will continue to install anyway, and just remain unactivated, we can sort key out after install.
Also, PC I am using right now has the same CPU & a 980, it isn't that old