HP Pavilion P6610f can no longer boot into Windows 10

[scifijeff]

Pavilion P6610f, Product # BM417AAR, Purchased 2011. 

DESCRIPTION OF BOOTING PROBLEM:

Error code: 0xc0000225
Have an HP Pavilion P6610f tower computer with 12GB RAM. Windows 10 will not boot; initially, as far as I got was a blue "Recovery" screen that said: "Your PC needs to be repaired. The application or operating system couldn't be loaded because a required file is missing or contains errors. File: \windows\system32\boot\winload.exe, Error code: 0xc0000225"; screen also says: "Press <Enter> to try again, Press <F8> for Startup Settings" - these don't work. So I performed another hard shutdown and then turned on computer, and pressed <ESC> key to bring up the BIOS menu, and selected Udrive (USB drive where I had created a Windows 10 Install Media/bootable thumb drive); computer then tried to boot off the USB drive and that failed too. On occasion, computer brings up Repair Mode blue screen which says: "Choose your keyboard layout" and "US" is already highlighted - but pressing <Enter> key does nothing; it's like computer is not even reading the keyboard. Have tried using a different keyboard that I know for sure works. Nothing. Then, using a different computer, I burned the Windows 10 64-bit ISO image onto dvd, and tried booting off this dvd. This failed as well, but now the blue Troubleshooting screen comes up, giving me access to the CMD prompt screen etc. I've tried all the initial options upon power-up: <ESC> brings up Boot menu to select booting from USB or DVD drive; <F10> brings up Setup menus (default is to boot first from DVD ROM drive) - but I can't find where to change Secure Boot to Disabled... as this will force computer to NOT boot from internal harddrive,  right? And boot from the DVD drive instead.

  I've searched online on this error code and how to fix it - opening CMD prompt and trying 6 methods for fixing it - none worked. 

  Btw, the system files (ike System32) and program files and my data (Documents) reside on my "D:" drive (I think my internal HD was partitioned between "C:" & "D:" back in 2011).

  I really need help as I don't know how to proceed from here... Thank You!!

[WAWood]

@scifijeff 

When you boot your PC and press F9, you should see a Boot Devices menu. 

With secure boot enabled, the only device it will show is the existing internal drive -- as that is done to make it SECURE. With that Disabled, it will show other devices, including a CD/DVD drive and connected external drives. 

But it won't BOOT from any of those unless you Disable secure boot, connect the device, and confirm that usingn F9. the Boot Devices menu shows that new device and allows you to select it.