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0x000000EDUNMOUNTABLE_BOOT_VOLUMEStop codeWidely reported

UNMOUNTABLE_BOOT_VOLUME (0xED): what it means and how to fix it

Updated Oct 10, 2026 · Checked against Microsoft documentation · How this page is made

Quick answer

UNMOUNTABLE_BOOT_VOLUME indicates that Windows attempted to mount your operating system storage drive during startup and failed. The crash typically points to file system corruption or a failing hard drive. The quickest first step is running Startup Repair from the Windows Recovery Environment.

What it means

What the stop code means

When Windows starts, the storage subsystem must locate, read, and mount the drive partition where system files reside. The stop code 0x000000ED appears when this mounting process fails completely. Because the operating system cannot mount the boot drive, it cannot load essential kernel components, and startup halts with a blue screen.

Under the hood, Windows records two critical parameters during this bug check. The first parameter specifies the device object assigned to the boot volume. The second parameter contains the status code returned by the file system detailing why the mount attempt was rejected.

Why Windows cannot mount the volume

Mount failures usually stem from two main sources: logical damage or hardware breakdown. Logical damage happens when the file system structure or the master boot record gets corrupted. When structures that define drive layouts become unreadable, Windows cannot interpret where partition boundaries start or finish.

Physical drive health is the other primary factor. When an OS boot storage device suffers physical hardware defects, bad sectors, or mechanical issues, the drive stops responding to basic input and output read commands. If Windows cannot read critical partition sectors during early boot, the storage driver returns an unmountable status code, producing bug check 0xED.

Common causes

  • Physical failure or hardware defects on the OS boot storage drive.
  • Corrupted file system structures preventing the partition from mounting.
  • Damaged master boot records or boot sectors on the primary drive.

How to fix it

Safest and most likely fixes first. Readers' answers to "Did this fix it?" reorder this list over time.

  1. Run Startup Repair

    Use this first when your computer fails to boot into Windows and opens the recovery screen.

    1. Turn on your computer and allow it to boot into the Windows Recovery Environment, or insert a bootable recovery USB drive or DVD.
    2. Select Troubleshoot on the Choose an option screen.
    3. Click Advanced options.
    4. Select Startup Repair to let Windows automatically detect and repair startup problems.
    Did this fix it?

  2. Repair the file system with CHKDSK

    Use this when Startup Repair cannot fix the boot volume and you suspect file system corruption.

    1. Open the Windows Recovery Environment from your hard drive or bootable recovery media.
    2. Navigate to Troubleshoot, then select Advanced options.
    3. Click Command Prompt.
    4. Type chkdsk /r and press Enter to locate bad sectors and recover readable information.
    5. Restart your computer after the process finishes.
    Did this fix it?

  3. Rebuild boot records with bootrec

    Use this from the recovery Command Prompt if corrupted boot records prevent the drive from mounting.

    1. Open the Windows Recovery Environment and go to Troubleshoot > Advanced options.
    2. Select Command Prompt.
    3. Run the bootrec command to repair the master boot record and boot records.
    4. Close the Command Prompt window and restart the computer.
    Did this fix it?

  4. Check the drive with manufacturer diagnostic tools

    Use this if repair commands fail and you need to confirm whether the hard drive has suffered a hardware failure.

    1. Use a separate working computer to check your hard drive vendor support page.
    2. Download the official bootable diagnostic tool provided by your hard drive manufacturer.
    3. Create a bootable USB drive or CD using the downloaded software.
    4. Boot your affected computer from the diagnostic media and run the drive self-test to check for hardware failure.
    Did this fix it?

Is it just you?

25+ Microsoft Q&A threads discuss this. Most recent activity:

Checked Oct 9, 2026. Refreshed automatically every few days.

Sources

Frequently asked questions

Can a failing hard drive cause UNMOUNTABLE_BOOT_VOLUME?

Yes. Physical drive failure is a primary cause of this bug check because damaged hardware prevents Windows from reading the partition.

What does CHKDSK /r do for this error?

Running CHKDSK /r scans the storage volume to identify bad sectors, fix logical file system errors, and recover readable data needed for boot.

What if Startup Repair fails to fix UNMOUNTABLE_BOOT_VOLUME?

If Startup Repair and command-line tools like CHKDSK and bootrec do not resolve the error, run hardware diagnostic utilities from your hard drive manufacturer to check if the drive has permanently failed.

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