The flash drive will need to be DOS or Windows bootable -- is it?

What model system?

Is there an administrator password on the system (which will lock out BIOS changes)?

I think I made it bootable. But I will double check that and post back. About the the admin password, there is no password for the BIOS.

Yes, the USB is bootable, I made it using uNetBootIn using the FreeDOS option. These are the only options I get in the boot options.

As you can see there is no Flash BIOS option.

If your UEFI does not have CSM then you won't be able to boot into a FreeDOS USB.

If your UEFI does have CSM, then you need to disable Secure Boot and enable Legacy CSM for you to be able to boot into a FreeDOS USB.

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From the screenshot you posted, it looks as if you need to go to Change Boot Mode Setting.

When I boot into FreeDOS, I get a C:\ prompt. Then I just run the BIOS executable.

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How do I check the CSM part? Whether I have it  or not? I was able to get to FreeDOS, but just couldn't locate the exe in the A drive.

That I can't tell you.

I have never had that problem before.

Are you the original owner?  The only possibility I can think of is that the BIOS is password protected.

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