- Software and systems
- Operating system
UNMOUNTABLE_BOOT_VOLUME
UNMOUNTABLE_BOOT_VOLUME (0xED) on Windows: the boot volume cannot be mounted
Risk level
High
Professional inspection is recommended.
Urgency
High
Quick answer
Windows tried to mount the boot volume and failed. Try Startup Repair from the recovery options and, if your files have no backup, do no more tests on the drive without IT support.
Safety first
Stop and check this first
- Do not format or reinstall Windows to fix 0xED before recovering your files: it erases the volume's contents.
Safe checks you can perform
- Startup Repair
- Copy your files before going further
- CHKDSK /r and bootrec from the recovery environment
Leave these tasks to a qualified professional
- Do not attempt this professional task: Drive diagnostics with the maker's tool
- Do not attempt this professional task: Mount status analysis
What a technician must be able to justify
A technician is coming
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Drive diagnostics with the maker's tool
What they doThe technician runs the drive maker's diagnostic tool to confirm or rule out a hardware fault.
They must show youthe diagnostic report with the drive result.
In writingwhether the drive failed and, if replaced, reference, capacity and reason.
Mount status analysis
What they doIf the crash is debugged, they use !analyze -v to read the file system status code in parameter 2.
They must show youthe status code and its meaning.
In writingwhat was repaired and how startup was verified.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Checks and evidence, step by step
Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
- 1
Startup Repair
No special tools
Procedure
- Who:
- you.
- How:
- in the recovery options go to Troubleshoot, Advanced options, Startup Repair. If they do not appear, create recovery media on another PC and start from the USB drive or DVD.
- Result that matters:
- whether Windows starts after the repair.
- If it starts:
- the problem was in the boot files; back up your data as soon as possible.
- If not:
- do not loop the repair; move on to file system repair with IT support.
- Evidence to keep:
- photo of any final repair message.
Evidence: Bug Check 0xED UNMOUNTABLE_BOOT_VOLUME
- 2
Copy your files before going further
No special tools
Procedure
- Who:
- you or IT support.
- How:
- if Windows starts even once, copy your important files to another drive before any other test.
- Result that matters:
- whether the files copy without errors.
- If they copy fine:
- you can continue with repairs at lower risk.
- If the copy fails or hangs:
- stop; the drive may be failing and the technician should decide how to recover the data.
- Evidence to keep:
- list of what was copied and what failed.
Evidence: Bug Check 0xED UNMOUNTABLE_BOOT_VOLUME · Troubleshooting Windows unexpected restarts and stop code errors
- 3
CHKDSK /r and bootrec from the recovery environment
Tools required
Procedure
- Who:
- IT support, or an experienced user with a backup done.
- How:
- from the Windows Recovery Environment command prompt run CHKDSK /r on the system volume and, if needed, bootrec to fix the boot records.
- Result that matters:
- whether CHKDSK repairs the file system and Windows starts again.
- If it starts:
- the damage was in the file system or boot record.
- If it fails or reports many errors:
- Microsoft says the drive may have failed; use the maker's diagnostics.
- Evidence to keep:
- CHKDSK and bootrec output.
If you have no backup, let IT support do it: a failing drive can get worse under long scans.
Evidence: Bug Check 0xED UNMOUNTABLE_BOOT_VOLUME
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- Software and systems
- Brand
- Microsoft Windows
- Product type
- Operating system
Known code variants
- 0x000000ED
- 0xED
- STOP 0x000000ED
- stop code UNMOUNTABLE_BOOT_VOLUME
- UNMOUNTABLE BOOT VOLUME
What it means
Microsoft defines 0x000000ED as the I/O subsystem failing when it tried to mount the boot volume. Parameter 2 holds the file system status code explaining why. According to Microsoft, it is typically related to a failure of the boot storage device, such as the hard drive. The code does not distinguish between a damaged file system, a broken boot record or a failed drive.
Warnings and stop conditions
- Higheditorial warning
Do not format or reinstall Windows to fix 0xED before recovering your files: it erases the volume's contents.
Evidence: Bug Check 0xED UNMOUNTABLE_BOOT_VOLUME
Symptoms and causes
Probable causes · in order
- Damaged file system or boot recordPossible
Told apart because Startup Repair, CHKDSK /r or bootrec get Windows starting again.
Evidence: Bug Check 0xED UNMOUNTABLE_BOOT_VOLUME
- Failed boot drivePossible
Microsoft says that if those steps fail, the hard drive may have failed; the drive maker's tools confirm it.
Evidence: Bug Check 0xED UNMOUNTABLE_BOOT_VOLUME
Virtual technician
Does UNMOUNTABLE_BOOT_VOLUME still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
- 1
Bug Check 0xED UNMOUNTABLE_BOOT_VOLUME
Microsoft · 2026 · official_doc
- 2
Troubleshooting Windows unexpected restarts and stop code errors
Microsoft · 2026 · official_doc
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