Windows 10: Windows 10 21H1 refuses to let me log in after upgrading from 20H2

I decided to upgrade from build 20H2 to build 21H1 but Windows now won't let me log into any user accounts, not even my own Microsoft account. The setup forced me to select the "Nothing" option when upgrading and now there's no way of logging into any user accounts. There simply aren't any accounts to log into. The setup didn't even prompt me to create a user account, but the most strange thing is that not even Microsoft accounts work. I tried opening the command prompt to use the net user add command but there is no way of opening cmd in the lock screen.

:)

 

Windows 10 upgrade problem, no input accepted

I really hate having to come here and ask for help, but I really am stumped. It hurts my geek pride. I have a PC with fairly modern hardware in it. It has a p8p67 pro in it. I have tried upgrading windows 10 on it twice now. Both times I have had the same result.

After windows finishes upgrading it goes to the log in/set up screen. I can't do anything. No keyboard or mouse input is accepted.

I will list some, or hopefully all, of the troubleshooting steps I have tried:

• Move keyboard and mouse to different USB ports.
• Try different keyboard or mouse.
• Restart computer, repeatedly.
• Google for related issues.
• Update Bios, because why not.
• Create boot media and revert to windows 7.

The windows 10 system restore boot media works fine with keyboard and mouse. All USB ports work in windows 7. I don't know what is wrong. I suspect that windows 10 is lacking a driver of some sort, but since the computer accepts no input I have no way of checking for which driver let alone installing it.

Please help me figure this out. If I have to revert back to windows 7 again, I am not going to get it upgraded to windows 10. Thank you in advanced.

 

KB5004476 Windows 10 2004 19041.1055, 20H2 19042.1055, 21H1 19043.1055 Win Update

Clicking on Task Scheduler Library.
The only mention of Edge in Task Scheduler that I can see I have already disabled.

 

Windows 10 upgrade problem, no input accepted

i've seen this when the stock USB drivers went kaput. Only ever seen it once - i used a PCI USB 2.0 card and connected the mouse and keyboard to that, and manually updated the USB 2/USB 3 drivers.