Partitions are corrupted

SIW2 said:

set csm to efi and bios

Launch CSM [Enabled]

Attachment 422586

Boot Devices Control [UEFI and Legacy OpROM]

Attachment 422587

F10 to save and exit

Thanks for the idea. I will see if I can implement it in my BIOS tomorrow.

- - - Updated - - -

Interesting ideas that I tried to implement. CSM support was already Enabled in BIOS. I did not find anything like "UEFI & Legacy OpRom" in Supermicro BIOS. On Boot Menu/Boot Mode Select is UEFI, though Legacy and Dual are choices.
\Boot\UEFI Application Boot Priorities Boot Option #1 I changed from Disabled to Built-in EFI Shell. No luck.

Supermicro tech: "And from the error message, it does not seem to be a bios issue. If you have this hardware running well last few years with same bios and configuration then it’s not a bios issue. It seems system was interrupted during boot at some point that caused the drive to loose it boot partition so it is not able to see the OS drive as a bootable device. If you have a blank drive somewhere, you should try installing the OS to see if there is any issue which will give you confirmation if there is a hardware issue."

When I try to do a clean Windows install, and select various partitions, I get this message:
"Window cannot be installed to this disk, which has MBR partition table. On EFI systems, Windows can be installed only on GPT disks."

Today I was able to to format and then convert physical disk 1 to GPT and then install Windows 10 Pro on that physical disk. However, no good news: system still boots to EFI Shell and no Windows boot manager in BIOS.
How does one "boot the installation media in bios mode"?

The mobo is a Supermicro from 2016. I got several replies from the tech there. When I have the Macrium Reflect USB stick attached, I do sometimes get two versions of it shown as in your picture. What difference does that make, since I assume both boot to the USB stick?

The key issue is that your BIOS shows, as does every normal BIOS, "Windows Boot Manager." But my BIOS still does not have that, even after a clean install of Windows 10 Pro. So the question is: how to get Windows Boot Manager seen by BIOS, since I assume it was installed on the hard drive. Since we don't have a capable tech in my area, I may have to sell this fine system with great hardware on ebay.
I liked your quotes from Curran and Abbey.

"setup.exe will only install in the same mode in which it was booted. if booted in uefi mode, it will refuse to install to an mbr partitioneddisk."

Just maybe this is an important insight. I have the Windows 10 install on a USB stick. I put it at the top of BIOS and booted into it and did Windows clean install, which completed.

So how can I boot into that Win 10 install usb stick in BIOS mode?

Or more to the point, how can I create a fat32 partition \EFI\MICROSOFT\BOOT\BOOTMGFW.EFI ?

SUPERMICRO MBD-X10DRI-O Extended ATX Server Motherboard.
My system was built around that mobo in 2016.