Software⏱️ 3 min read📅 2026-06-19

How to Fix: How do I fix an issue with Disk Manager that is causing a Windows Boot Manager Error?

Windows Boot Manager Error caused by accidentally making C: drive active in Disk Manager. Possible solution involves using bootrec /fixmbr and bootrec /fixBoot commands.

Quick Answer: Try running the missing bootrec /fixBoot command with administrator privileges to fix the issue.

📋 Table of Contents

  1. 💡 Why You Are Getting This Error
  2. ✅ Best Solutions to Fix It
  3. 💡 Conclusion

A Windows Boot Manager Error has occurred due to an incorrect action taken in Disk Manager, causing issues with booting. This error affects users who have made changes to their disk configuration without proper understanding of the consequences.

This issue is frustrating because it prevents the user from accessing their operating system and can lead to data loss if not addressed promptly. In this troubleshooting guide, we will walk you through the steps to resolve the issue without losing any files.

💡 Why You Are Getting This Error

  • The primary reason for this error is that the C: drive was mistakenly made active in Disk Manager, which has corrupted the boot configuration of Windows 10.
  • Another possible cause is that the E drive was incorrectly configured as a boot device, even though it does not have an operating system installed.

✅ Best Solutions to Fix It

Re-configure Boot Order and Fix Boot Configuration

  1. Step 1: Open Disk Manager and identify the C: drive as the active disk. Right-click on it and select 'Change Drive Letter and Paths'. Remove any existing drive letter assigned to the C: drive.
  2. Step 2: Next, open Command Prompt with administrator privileges (right-click on Start > Command Prompt (Admin)). Type `bootrec /fixmbr` and press Enter to fix the master boot record. Then, type `bootrec /fixBoot` but do not execute it yet.
  3. Step 3: Now, go back to Disk Manager and identify the C: drive as the active disk again. Right-click on it and select 'Change Drive Letter and Paths'. Assign a new drive letter to the C: drive (e.g., D:).

Re-create Boot Configuration using Bootrec

  1. Step 1: Open Command Prompt with administrator privileges. Type `bootrec /list` and press Enter to list all boot devices. Identify the disk number of the C: drive (it should be listed as Disk #1).

💡 Conclusion

To summarize, the issue can be resolved by re-configuring the boot order and fixing the boot configuration using Bootrec. By following these steps, you should be able to regain access to your operating system without losing any files.

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