Converting to UEFI isn't as easy as just enabling UEFI. The boot disc must also be formatted in "GPT" rather than MBR which is used with Legacy (NON UEFI) BIOS.
@Lobster44 UEFI boots in a fundamentally different way from Legacy BIOS. With Legacy BIOS, you boot from a device, because executable code can be stored at defined sectors of the device you’re booting from. And that’s why you can just choose to boot from a device. UEFI doesn’t work like that. It instead boots from a specific bootloader FILE located on a specific partition of a specific device, and the path to that file actually has to be registered into the firmware. To facilitate temporary boot needs such as from external USB devices, the UEFI spec defines a standard path of \EFI\Boot\Bootx64.EFI, which systems can look for, but the Windows Boot Manager instance for installed Windows environments doesn’t use that. Instead, Windows Setup handles registering a suitable boot option into the firmware. But as noted by @fireberd above, if you plan to just boot an existing Windows environment in UEFI mode as opposed to making this change before performing a fresh install, you cannot simply switch your system to UEFI mode and call it a day. For one thing, even if you knew the path to that bootloader file, it wouldn’t currently exist on your disk that Windows has currently set up for Legacy BIOS mode. The appropriate method would be to use Microsoft’s MBR2GPT utility, which despite the name does a lot more than convert your disk from MBR to GPT. It also creates the additional partitions necessary for UEFI booting, and should also handle that registration. Microsoft has documentation for that tool that should come up if you just Google that name, but essentially, you run that utility FIRST, and then if it confirms success, you switch your system to UEFI mode so that Windows will boot the next time. Doing both parts in that order matters, because your existing Windows installation won’t boot in UEFI mode if you just switched your system over, but after the conversion completes, the converted installation won’t boot in Legacy BIOS mode again, so you HAVE to switch at that point..
If the system boots in legacy mode, the drive is partitioned in MBR mode. While there are ways to convert to GPT (which UEFI requires), it's much safer and cleaner to simply reinstall Windows in UEFI mode.
When you do this, the operating system will be installed such that the drive will be UEFI bootable.
OK, so it looks like what I have to do is wipe the system (or just start with a new drive) and use the MBR2GPT utility to format the drive to GPT, then go from there.
Yes, I thought it was just an easy switch in the BIOS. I didn't know it was more involved than that.
fireberd
9 Legend
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33.4K Posts
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October 14th, 2021 11:00
Converting to UEFI isn't as easy as just enabling UEFI. The boot disc must also be formatted in "GPT" rather than MBR which is used with Legacy (NON UEFI) BIOS.
Convert MBR Disk to GPT Disk in Windows 10 | Tutorials (tenforums.com)
jphughan
9 Legend
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14K Posts
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October 14th, 2021 15:00
@Lobster44 UEFI boots in a fundamentally different way from Legacy BIOS. With Legacy BIOS, you boot from a device, because executable code can be stored at defined sectors of the device you’re booting from. And that’s why you can just choose to boot from a device. UEFI doesn’t work like that. It instead boots from a specific bootloader FILE located on a specific partition of a specific device, and the path to that file actually has to be registered into the firmware. To facilitate temporary boot needs such as from external USB devices, the UEFI spec defines a standard path of \EFI\Boot\Bootx64.EFI, which systems can look for, but the Windows Boot Manager instance for installed Windows environments doesn’t use that. Instead, Windows Setup handles registering a suitable boot option into the firmware. But as noted by @fireberd above, if you plan to just boot an existing Windows environment in UEFI mode as opposed to making this change before performing a fresh install, you cannot simply switch your system to UEFI mode and call it a day. For one thing, even if you knew the path to that bootloader file, it wouldn’t currently exist on your disk that Windows has currently set up for Legacy BIOS mode. The appropriate method would be to use Microsoft’s MBR2GPT utility, which despite the name does a lot more than convert your disk from MBR to GPT. It also creates the additional partitions necessary for UEFI booting, and should also handle that registration. Microsoft has documentation for that tool that should come up if you just Google that name, but essentially, you run that utility FIRST, and then if it confirms success, you switch your system to UEFI mode so that Windows will boot the next time. Doing both parts in that order matters, because your existing Windows installation won’t boot in UEFI mode if you just switched your system over, but after the conversion completes, the converted installation won’t boot in Legacy BIOS mode again, so you HAVE to switch at that point..
ejn63
10 Elder
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30.5K Posts
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October 14th, 2021 18:00
If the system boots in legacy mode, the drive is partitioned in MBR mode. While there are ways to convert to GPT (which UEFI requires), it's much safer and cleaner to simply reinstall Windows in UEFI mode.
When you do this, the operating system will be installed such that the drive will be UEFI bootable.
Lobster44
1 Rookie
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3 Posts
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October 17th, 2021 19:00
Thanks for all the info everyone.
OK, so it looks like what I have to do is wipe the system (or just start with a new drive) and use the MBR2GPT utility to format the drive to GPT, then go from there.
Yes, I thought it was just an easy switch in the BIOS. I didn't know it was more involved than that.
Thanks again for all the help. Appreciate it.