Normally this is called CSM but the firmware is old. Often in UEFI firmware this is not a hard drive setting but a UEFI firmware setting that allows Legacy installs to MBR disks without UEFI.
And what are the other settings choices? If the wiped drive converted to MBR doesn't succeed, then try UEFI and then see if the DVD drive shows up in BIOS Boot Menu Key as a UEFI device.
Normally deleting all partitions will suffice for the installer to reset formatting GPT<>MBR.