I have switched Windows 10 installations from UEFI to BIOS. It works fine. A customer wanted to be able to press the normal keys on bootup to choose boot device. UEFI doesn't allow that.
Think of it this way. In order to access UEFI settings you have to access them from a booted Windows installation. But if Windows crashes then you lose access to those settings, don't you? It's just a flaky system that protects no one.
It's like the Windows change between XP and 7. To the applauding choruses of computer critic drones bought and paid for by Microsoft, the superiority of the Windows 7 repair techniques were trumpeted across the land. All the computer magazines, all the tech websites spouted identical words in unison (a clue they came from the Microsoft muse), "Windows 7 has much better repair tools if your Windows installation goes bust!!!!"
But in fact, system startup repair was and is a black box. "Windows is repairing your system. If it works you'll be able to boot normally after this is done. The procedure may take a long time." That's the sum total of your information and nothing is done to give YOU any useful information which may be used to repair the installation. Not only that but Windows XP used to have a repair install procedure. You put the original install disk in the drive, select Repair Install and Windows is reinstalled, saving all your programs and settings. In Windows 7 and above that option is gone! Instead, you can only access repair install if you do it from your running Windows system. Guess what? If Windows ran you WOULDN'T NEED A REPAIR INSTALL.
Non-existent security. Removal of user options. Severe feature cutbacks. That's Microsoft. The answer is Linux. Steam now has over 3000 commercial games natively working in Linux, 1000 of them released just in the past month. Over a million Steam customers own and play Linux version games. Just released Wine 2.2 runs Fallout 3 and 4 flawlessly. In Linux, no soulless corporation will hunt you down and serve you a lawsuit for publishing a repair disk that actually works.
By the way, I found a great and free Microsloth Windoze repair tool called
Lazesoft Recovery Suite. Has many tools that Microsoft doesn't want you to have. Grab it quick before they are sued into oblivion by the company who has your back and cares about your computing experience. With it you can even make, save and restore disk images, just like Acronis True Image! It also has genuinely informative and effective startup repair tools. That alone means Microsoft cannot tolerate their existence.