I'm trying to enable Secure Boot to update to Windows 11, but I'm running into issues. My current Windows 10 setup is in legacy/CSM mode, and when I turn on Secure Boot, my OS won't boot. I attempted to run the command 'mbr2gpt /validate /disk:X /allowFullOS' but I received an error. My OS is located on drive 3, which is only my C: drive, and doesn't seem to have other partitions. Do I need to shrink the partition by 300MB for the command to work? After that, can I simply use 'mbr2gpt /convert /disk:X /allowFullOS' to convert it? Is there any risk of data loss or corruption of my C: drive? Once everything is done, can I enable Secure Boot in BIOS and expect Windows 10 to boot up properly so I can upgrade to Windows 11?
2 Answers
Before making any changes, make sure to back up your data! Changing your BIOS settings or disk setup can lead to data loss. You need to switch to UEFI mode to enable Secure Boot, which means your existing Windows 10 installation won’t boot anymore. I'd recommend wiping the drive and doing a fresh install of Windows 11 after setting up the BIOS correctly.
Yes, you can use your current activation key to activate Windows 11 after a fresh install.
Enabling Secure Boot requires converting your system to UEFI, which is why your Windows won't boot with it enabled. Unfortunately, you can't just convert your current Windows 10 installation to UEFI seamlessly. It's usually safer to back up, wipe the drive, and reinstall.

Can I still use my current Win10 activation key for Windows 11 after the fresh install?