trying to boot from a non-HDD device

[rxt1885]

My HD BIOS is corrupt or useless -- after the PC starts up, it can't sign in using the camera or a PIN (this seems to be part of the corruption; the PIN and camera worked before). In an event, I assume I need to boot off of another media, e.g., a thumb drive, a USB drive. But that's what I can't do, and when I get into the BIOS settings, it won't let me specify a non-HDD boot drive first -- it's as if the HDD boot drive is hard-coded as  having to be first. Why? What can I do?

[WAWood]

Windows 11 devices nearly always have Secure-Boot (in the BIOS) enabled by default. When that is the case, you can not boot from anything other than the internal drive.

You have to go into the UEFI settings and disable secure-boot.  It is usually shown on a Security tab.

Good Luck

[rxt1885]

now that it's disabled, how do I boot to a 'virgin' PC? can I create a useful file from a sister PC? 

[WAWood]

I don't understand the question. Disabling Secure Boot will not prevent the PC from booting; instead, it will allow it to boot from a USB stick.

[RXT-1885]

Sorry, right. Perhaps my question is simplistic: what can I put on the stick to fix things? I don't have any restore, etc. files from the broken PC

[RXT-1885]

Sorry, I do know how to access the command prompt from the broken PC to actually access files. Are there files there?

[WAWood]

What you describe is STANDARD behaviour for new PC that have Secure Boot enabled in the UEFI settings -- which any Windows 11 PC will have BY DEFAULT.  This is NOT an indicates of any BIOS corruption; instead, this is the way it is supposed to work!

To boot of anything other than the internal drive, you have to go into the UEFI settings and disable secure boot.  That is usually located in the Security tab of the UEFI settings.