If when you’re trying to back up your Windows 10 operating system on an external drive, and you receive the error message; Bitlocker Drive Encryption cannot be used because critical BitLocker system files are missing or corrupted with error code 0x8031004A, then this post is intended to help you. In this post, we will identify the possible cause, as well as provide the appropriate solution you can try to help you resolve the issue.

When you encounter this issue you receive the following error message;

BitLocker Drive Encryption cannot be used because critical BitLocker system files are missing or corrupted. Use Windows Startup Repair to restore these files to your computer. (0x8031004A)

The problem consists of corrupted data on your external drive, data due to which the back up cannot proceed.

Fix BitLocker Drive Encryption error 0x8031004A

If you’re faced with this BitLocker Drive Encryption error 0x8031004A issue during the back up of Windows 10 OS, you can try either of the two recommended solutions outlined below and see if that helps.

1. Use DiskPart to clean and re-create the partition on the external drive
2. Disable and then enable Windows RE (Recovery Environment)

Let’s take a look at the description of the steps involved as it concerns each of the solution.

1] Use DiskPart to clean and re-create the partition on the external drive

To use DiskPart to clean and re-create the partition on the external drive, do the following:

Before you begin, you can back up the contents of the external drive to another drive.

• Press Windows key + R to invoke the Run dialog.
• In the Run dialog box, type cmd and then press CTRL + SHIFT + ENTER to open Command Prompt in admin/elevated mode.
• In the command prompt window, type diskpart and hit Enter.
• Next, type list disk and hit Enter.

You should now see a list of all drives on your computer. Find the one that is causing the issues and note the number.

• Next, type in select disk #, where # is the number of the drive and hit Enter.
• Next, type clean and hit Enter.

You should get a message saying DiskPart succeeded in cleaning the disk. This will delete all of your data on the drive.

Now that you have cleaned the disk, you can proceed to create a new partition.

• Now, type the command below and hit Enter.

create partition primary

• Next, assign a letter to the drive by typing the command below and hit Enter. Where X is the letter you want to assign.

assign letter = X

Now that you’ve assigned a letter, you should format the partition so you can use it.

• Type in the command below and hit Enter. Note that fs=ntfs means that the partition will be formatted in the NTFS filesystem, and if that doesn’t suit your needs, you can use fs=fat32 instead to get a FAT32-formatted filesystem.

format fs=ntfs quick

Once the format operation completes, you should now have your external drive up and running, and you can back up your Windows 10 operating system on it without encountering the BitLocker Drive Encryption error 0x8031004A. Otherwise, try the next solution.

2] Disable and then enable Windows RE (Recovery Environment)

To disable and then enable Windows RE, do the following:

• Open an elevated/admin Command Prompt.
• In the command prompt, copy and paste (assuming the C drive is housing the Windows 10 installation) the command below and hit Enter to disable Windows RE:

C:\Windows\System32\REAgentC.exe /disable

• Now, disconnect the external drive.
• Next, copy and paste the command below and hit Enter to enable Windows RE:

C:\Windows\System32\REAgentC.exe /enable

You can now reconnect the external drive to the computer and try the OS back up again and see if the issue is resolved.

Hope either of this solution works for you!