I wanted to convert an MBR/BIOS boot drive to GPT/UEFI, but without needing to decrypt and then re-encrypt Bitlocker. Mainly because I am lazy. This worked, but I’ll warn that the advice to decrypt completely first is without any doubt the safest way to go.
With the following changes:
- Print out your Bitlocker Recovery Key from Control Panel, Bitlocker. You will need this key.
- Take a backup. No seriously. Use Veeam Endpoint if you don’t have anything else installed to take backups. Stuff goes wrong with computers, and you don’t want to lose your system installation and data.
- Suspend Bitlocker protection on your system drive.
- Reboot from your Windows installation / recovery DVD/USB, verify that you can get to your c:\windows directory. This might be d:\windows if you have a recovery partition at the end of the disk.
- Now boot into Windows and convert to GPT using gptgen
- When you then boot into the Windows installation / recovery media, you’ll be asked for the Bitlocker Recovery Key. After that, the rest of the steps are as in the generic instructions.
- When booting into Windows (assuming you changed your BIOS to boot (U)EFI instead of MBR now), you’ll be asked for the recovery key again.
- In my case, the drive didn’t show suspended. I suspended it again.
- After that, resuming Bitlocker encryption will fail with “The System cannot find the file specified”.
- Open Explorer, navigate to C:\Windows\System32\Recovery and rename the file “ReAgent.xml” to “ReAgent.xml.old”
- Resume Bitlocker encryption on drive C:\ This should now succeed.
- Reboot for good measure to verify that everything works and you don’t get prompted for the recovery key any more.