Rightek Rescue · Guides · Unmountable Boot Volume
UNMOUNTABLE_BOOT_VOLUME? Read this before you run chkdsk
Windows located your drive, started to read it, and could not mount the filesystem on it. That has two very different causes: a filesystem that needs repairing, or a disk that is failing. The standard internet advice for this stop code is the same command in both cases — and in the second case it can be what finally kills the drive.
What you're seeing
- A blue screen reading UNMOUNTABLE_BOOT_VOLUME, stop code
0x000000ED - It happens early — usually before you ever see a sign-in screen
- Often after an unexpected shutdown or power cut, a failed update, or moving the drive to another machine
- Sometimes alongside slow boots, freezes or odd noises in the weeks beforehand
Why it happens
Three causes, and telling them apart matters more than fixing any of them:
- Filesystem corruption. The NTFS structures that describe where files live are inconsistent — typically after a power loss mid-write. The disk is healthy; its bookkeeping is not. This repairs cleanly.
- A physically failing drive. Bad sectors have landed on the structures Windows needs to mount the volume. The bookkeeping looks corrupt because the disk can no longer reliably read it back. This does not repair cleanly, and repair attempts make it worse.
- Damaged boot configuration. Less common for this specific code, but a corrupt BCD or a drive moved to different hardware can produce it.
⚠ Why the usual advice is risky here
Search this stop code and nearly every result tells you to run chkdsk /r.
/r reads and rewrites every sector on the disk, for hours. On a
healthy drive that is fine. On a drive that is failing, hours of sustained load on already-weak
media is exactly the wrong thing to do, and it is a common way that recoverable data becomes
unrecoverable. Establish which drive you have before you run it, not after.
What to do — the options and their limits
Step one: work out whether the drive is healthy
This is not optional and it is not hard. Any of the following means treat it as failing:
- Noise. Clicking, grinding, or a repeated spin-up-and-stop on a mechanical drive. An SSD is silent, so this only tells you about spinning disks.
- History. Windows had shown a "hard disk problem" warning, or the machine had been freezing for seconds at a time before this happened.
- The firmware cannot see it reliably. Enter the BIOS/UEFI (usually Del or F2 at power-on). A drive that appears sometimes and not others is failing, not corrupt.
If any of those are true: power it off and stop. Get the data copied off before anything else. That is a recovery job — either from a rescue USB that reads the disk without writing to it, or on a bench. We do the bench version.
Step two: if the drive looks healthy, repair the filesystem
Get into the Recovery Environment — hold the power button to force a shutdown, power on, repeat three times, and Windows opens Recovery on the fourth. Then Troubleshoot → Advanced options → Command Prompt.
Your Windows drive is usually not C: in here. Run diskpart, then
list volume, then exit, and note the letter with the Windows folder on it.
Then:
chkdsk D: /f— fixes filesystem structure without the full-surface scan. Minutes rather than hours, and far gentler. Try this first, always.- If Windows now boots, stop. Do not run the deeper scan for tidiness.
- Only if
/fcompletes cleanly and it still will not boot is/rworth considering — and only once you have a copy of anything you cannot lose.
Step three: if it is the boot configuration
Advanced options → Startup Repair rebuilds boot files automatically and is safe to run. It is worth one attempt before anything more involved.
What none of this fixes
If chkdsk /f reports errors it cannot correct, or the volume will not mount even
after a clean scan, the filesystem damage has reached the structures needed to describe the disk
itself. At that point repairing in place is no longer the goal — getting the data off is.
Do that before any further attempts.
⚡ The one-click way: let Rightek Rescue do it
Rescue reads the drive's own health data first and flags a disk that shows signs of failing, so you can copy your data off before anything else. If the disk is healthy, it repairs the filesystem and the boot configuration without the hours-long surface scan. On any working PC: download Rescue, put it on a USB (one click makes it bootable), boot the affected PC from it, and choose Fix My PC. The diagnosis is free and it tells you what it found before it changes anything.
FAQ
Is UNMOUNTABLE_BOOT_VOLUME always a dying hard drive?
No, and assuming either answer is the mistake. It is often plain filesystem corruption on a perfectly healthy disk, usually after a power cut. But it is also one of the codes a failing drive produces, which is why checking the drive's health before running repairs matters more than the repair itself.
Everyone says to run chkdsk /r. Why do you say not to?
Because /r reads and rewrites every sector on the disk over several hours. On a healthy drive that is harmless. On a drive that is already failing, sustained load on weak media is a common way that recoverable data becomes unrecoverable. Run chkdsk /f first, which is quick and fixes the usual cause, and only consider /r once you know the disk is sound and your data is copied.
Can I get my files off if Windows will not boot at all?
Usually yes. The files are still on the disk — what is broken is Windows' ability to mount the volume, not the data itself. A rescue USB reads the drive from outside Windows and copies the files to another disk without writing to the failing one.
How do I know if my SSD is failing? It does not make noise.
You cannot hear it, so you have to read it: an SSD reports its own wear and error counts through S.M.A.R.T. data. Warning signs from the outside are files that fail to read, the drive dropping out of the BIOS intermittently, or the machine freezing for seconds at a time.
Which Windows versions does this apply to?
Windows 10 and 11. The stop code is much older, and the reasoning applies equally to earlier versions, but Rescue itself supports 10 and 11.