I recently built a new PC using an AMD Ryzen 7 9800X3D processor and a Gigabyte B850 AORUS ELITE motherboard. I upgraded from an older Intel 8700k system, which worked perfectly. However, now when I try to boot my new PC, I encounter an error and it defaults into the BIOS instead of loading Windows from my NVME drive that has Windows 11 installed. The BIOS sees the NVME connected, but it doesn't recognize it as a bootable device. I initially received an error message, pressed 'Y' to continue, but that just sent me to the BIOS. After enabling CSM in BIOS, the NVME appeared as bootable, but then I encountered another error. I managed to boot from an old HDD with Windows using an external HDD bay, and I can access the NVME files through Windows Explorer, although the icon appears strange. I've tried loading default BIOS settings, updating the BIOS, swapping the NVME to a different slot, and changing the BIOS settings between UEFI and Legacy, but nothing has resolved the issue. I suspect Bitlocker is causing the problem and I'm hoping to find a solution before resorting to formatting the NVME and reinstalling Windows.
2 Answers
It sounds like your old drive might be set up in legacy MBR format. To fix this, you need to clone your current drive onto another SSD or HDD, switch your old drive to GPT format, and clone everything back. There are tutorials online that can guide you on how to change from MBR to GPT, which should help with the boot issues you’re facing.
The issue with Bitlocker is that it prevents unauthorized access if someone tries to move your drive to another PC. It's possible that you might need your recovery key to proceed. Since you can access your old Windows installation on the HDD, one option you could try is to disable Bitlocker completely, which means decrypting the files on your NVME. If there's not much critical data on the NVME, reinstalling Windows might actually be quicker.

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