Note that my post said “old drives” - plural. Mint was being installed on a secondary, formatted drive, and refused because that drive was not GPT-formatted (that record exists outside of the filesystem formatting). At the time, the BIOS was not set to force UEFI, so this was Mint’s decision, not the BIOS’s, and I don’t understand it. I left Windows alone on a different drive.
Believe me, I did plenty of reading up on BIOS UEFI settings just to resolve the issue. I still don’t claim to be a master, but I at least know enough to express how annoying the reconfiguration can be - independent of which OS you’re choosing.
Actually no. It’s not Mint’s decision whether to start the install USB with UEFI or BIOS. It actually depends on what the firmware chose to start and how the install medium is formatted. Some install media is only setup for BIOS booting, some for only UEFI, and some can do both. If the firmware detects the medium as supporting both then it should choose UEFI first but this depends on what settings you have in the firmware, and if you choose an option at a boot menu as boot menus allow you to override the default. When it comes to actually installing the OS most sane installation software will look at how it booted and install that way. So if it detects it was starting with UEFI it will configure the install to be UEFI, same if it was started with BIOS it will install as BIOS. How does it know? UEFI variables are one way. They can normally only be accessed if the system was started with UEFI.
If you truly wipe a drive you wipe the partition table as well. You say the table is outside the file system formatting, and this is sort of true, but they are both just data on the disk. Disk don’t care where the partition table ends and the file system begins. In fact you don’t even need a partition table at all. Unlike some other systems Linux will let you put a file system straight on the disk, the whole disk, with no partition table in sight. It’s not recommended mind you, because it will freak Windows out if it sees it. Windows will see it as a blank disk and not so helpfully offer to format the thing. When I say format a disk, I mean the whole thing, partition table and all. It’s also not possible to make a partition tableless disk bootable in UEFI. In BIOS it’s possible though as BIOS doesn’t read partition tables. It just needs a boot sector and that’s it.
Also if you’re trying to change a disk from MBR to GPT, and you don’t care about data, you shouldn’t be converting it. You should be formatting/wiping the whole thing and making a new partition table. Which is normally what it offers to do if you tell it to erase everything and install it.
Edit: Getting down voted for actually knowing how computers work and bothering to explain it. Shock horror.
