Hello, Thank you for posting in Q&A forum. There is a known conflict with the Deny write access to fixed drives not protected by BitLocker Group Policy setting located in Computer Configuration\Administrative Templates\Windows Components\BitLocker Drive Encryption\Fixed Data Drives. When this policy setting is enabled, if you attempted to merge an existing drive into the system drive, the tool will fail to copy the required boot file onto the target drive to create the system drive. The following error message is displayed: BitLocker setup failed to copy boot files. You may need to manually prepare your drive for BitLocker. Meanwhile you can also manually prepare your drive for BitLocker by following below Microsoft Documentation: https://support.microsoft.com/en-us/topic/description-of-the-bitlocker-drive-preparation-tool-3a4bb87b-6f72-733f-b448-c2b45412445a Best Regards, Hania Lian
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