My computer shows a "Kernel Security Check Failure" during startup and fails every time. I can't reach Windows or Safe Mode, although I can open the UEFI settings. I'm not very technical, so I'd appreciate straightforward troubleshooting steps. I've also seen another error screen appear during the failed startup.
2 Answers
Since you can still enter UEFI, try loading the BIOS/UEFI default settings and save the changes. Don’t change boot or storage settings manually unless you know what they do, because the wrong setting could prevent Windows from being found.
Start by unplugging every external device you don’t need—USB drives, printers, controllers, hubs, and similar accessories—then try booting again. A faulty peripheral or USB device can sometimes interfere with startup.

Related Questions
Can't Load PhpMyadmin On After Server Update
Redirect www to non-www in Apache Conf
How To Check If Your SSL Cert Is SHA 1
Windows TrackPad Gestures