Booting to non-UEFI USB failing, is BIOS my problem?

I have an HP Spectre that I am trying to load with Windows 7 on an MBR partition table. I can successfully load Windows 7 using EFI with GPT partition table, but not MBR.

With BIOS Legacy mode on:
When booting to USB via UEFI -> Windows 7 will install on GPT only
When booting to USB via non-UEFI -> Windows 7 installer will not load "Reboot and Select proper Boot device"

From all forums I can find, non-UEFI is supposed to work with Legacy Mode on. But it does not. Do newer BIOS block true legacy mode?

This seems possible for me, if you have set all BIOS options to DEFAULT.
What about the option “Secure Boot”? If it should be enabled by default, disable it and try to boot again in LEGACY mode.

Yes, when Legacy mode is ON, secure boot automatically turns OFF. I can’t find any other options in the BIOS.

The problem was the USB needed to be formatted with NTFS rather than FAT32.