Cannot boot into BIOS with F2 or boot from CD or USB flash drive

For some unknown reason, for the past couple of days, I can only boot my ASUS X750JA laptop normally into Windows 10 (Home). Previously, after Shift+Restart, I used to be able to enter BIOS setup with F2. Now, whenever I try this, the screen remains black and nothing happens: the disk LED does not even flicker!
In future, to restore a system partition backup if anything goes awry with my Windows 10 installation, I need to be able to boot up from a bootable USB flash drive or CD-ROM including software such as AOMEI Backupper or Terabyte Image for Windows. But how will I ever be able to do that if I can't get into BIOS to enable Launch CSM, disable Secure Boot Control and then set the desired boot priority? I seem to be scuppered.
Also, I have successfully made a Windows 10 System Image, but when I practice restoring it from the Advanced Startup screen (just because I want to know how this works in advance of any problems), I again get stuck in a black screen with no disk activity.
Additionally, I tried to make a Windows Recovery USB flash drive, starting from Recovery in the Control Panel. Even though I click the option "Back up system files to the recovery drive", which should add several GB, all that's been written to the flash drive is the basic WinRE package.
It seems as if everything I'm trying to do is being blocked by the M$ demons. This is exacerbating my paranoia.
Can anyone help? Ahead of the Anniversary Update, I want to know that I can restore my EFI system and C partitions if anything goes wrong ... or indeed at any point in the future.

F2 should not be required :

UEFI Firmware Settings - Boot to from inside Windows 10 - Windows 10 Forums

There is also a program called EasyUEFI that sets the option to boot into UEFI

http://www.easyuefi.com/

Hi NavyLCDR,
I already tried that method via the Advanced Startup screen. After clicking on Troubleshoot then UEFI Firmware settings I just got a black screen. No Restart button to click. :-( Then, when I restart, the laptop boots normally into Windows 10. Nothing is working for me. I'll try EasyUEFI next. Thanks.
Can anyone else offer a solution?
Cheers, Rob

robst247 said:

Thanks.Can anyone else offer a solution?
Cheers, Rob

Turn off Windows 10 fast startup:
Fast Startup - Turn On or Off in Windows 10 - Windows 10 Forums

With fast startup turned on, when you turn off your computer and it does not shut down all the way back to a complete 100% UEFI startup and, therefore, you won't have the opportunity to tap the key to enter UEFI setup. If you turn off fast startup, it shuts down the computer 100% all the way every time and then when you start it back up tapping the key to enter UEFI setup should work. It depends on your specific computer which key it is to enter UEFI setup.

I've tried disabling Fast Boot and I've tried EasyUEFI as you suggested, but nothing works! All I can do is boot normally into Windows 10. According to the ASUS manual for this laptop, BIOS can be entered by pressing F2 on startup and Advanced Startup can be entered by pressing F9 on startup. Until a couple of days ago, F2 got me into the BIOS. But now, whatever I do - trying to access BIOS, UEFI or Restore System Image - I always get into that dead-end black screen and zero hard-disk activity.
With EasyUEFI, I did manage to create a CD-ROM boot entry and give it top priority, but on rebooting - even though the CD-DVD drive span up and the bootable disk was being read - the laptop started up normally into Windows 10. Nothing I try works; I'm getting totally frustrated. It's as if there's a lock on the computer blocking all options except normal startup.
I did read someone that if Secure Boot Control is enabled, you cannot boot from a USB stick or CD-ROM. Previously, I managed to disable Secure Boot Control after entering the BIOS with F2, but that no longer works! I'm stuck, and I have no idea how to remedy this.

robst247 said:

I did read someone that if Secure Boot Control is enabled, you cannot boot from a USB stick or CD-ROM. Previously, I managed to disable Secure Boot Control after entering the BIOS with F2, but that no longer works! I'm stuck, and I have no idea how to remedy this.

I know little about Secure Boot, but I have booted from a USB drive to do a clean install of 10 on a UEFI system. Without changing the UEFI settings from their defaults.

Not sure what to suggest. Have you cleared the CMOS? (That's one way to assure that fast boot is off; it usually is in the default UEFI settings.)

I finally solved the problem by flashing the BIOS to the latest version from within Windows 10 (using the ASUS WinFlash utility). Then after shutting down and pressing the power button, I managed to enter the BIOS setup screen - finally! - by repeatedly pressing F2 rather than keeping it depressed. (This, on the advice of ASUS phone support.) I then restored the standard BIOS settings using F9, enabled Launch CSM and disabled Secure Boot. Now everything's working perfectly! What a relief!