- Software and systems
- Operating system
INACCESSIBLE_BOOT_DEVICE
INACCESSIBLE_BOOT_DEVICE (0x7B) on Windows: the system lost access to the boot partition
Risk level
High
Professional inspection is recommended.
Urgency
High
Quick answer
Windows stopped during startup because it lost access to the system partition. If you just changed a drive, a disk controller or a UEFI (BIOS) setting, undo that change before you try anything else.
Safety first
Stop and check this first
- If the repair screen offers to reinstall or format, do not do it without a copy of your files: 0x7B alone does not prove the drive is damaged, and a clean install erases data.
Safe checks you can perform
- What changed right before the first crash
- Recently added hardware
- Start in Safe Mode
- System Restore from the recovery options
Leave these tasks to a qualified professional
- Do not attempt this professional task: Review the storage configuration
- Do not attempt this professional task: Analyse startup with a debugger or the maker's diagnostics
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.
Review the storage configuration
What they doThe technician identifies which controller the boot drive sits on (SATA, IDE or other), what else shares it and which file system it uses, and checks drive, controller and firmware compatibility with your Windows version.
They must show youthe controller model, the loaded driver and the firmware or UEFI version.
In writingwhich incompatibility or change they found and what they adjusted.
Analyse startup with a debugger or the maker's diagnostics
What they doWith the kernel debugger they check whether disk, partmgr, NTFS, classpnp, pci and the controller driver loaded (lm, !devnode 0 1), or run the system maker's hardware diagnostics on the drive.
They must show youthe debugger output or the diagnostic report with the drive result.
In writingwhether the drive passed and, if replaced, the part reference and reason.
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
What changed right before the first crash
No special tools
Procedure
- Who:
- you.
- How:
- note the date of the first blue screen and list whether that day you installed a drive or controller, changed UEFI (BIOS) settings or repartitioned. If you changed the controller mode, set it back.
- Result that matters:
- whether Windows starts again once the change is undone.
- If it starts after undoing it:
- that change was the cause; ask the drive or motherboard maker before repeating it.
- If nothing changes:
- the change does not explain it alone; go to the next check.
- Evidence to keep:
- a photo of the code on screen and a dated list of changes.
Evidence: Bug Check 0x7B INACCESSIBLE_BOOT_DEVICE · Troubleshooting Windows unexpected restarts and stop code errors
- 2
Recently added hardware
No special tools
Procedure
- Who:
- you, with the PC shut down and unplugged.
- How:
- remove only what you added yourself and can unplug without tools (external USB drives, memory cards) and start again.
- Result that matters:
- whether the error goes away without that device.
- If it goes away:
- that device or its settings interfere; ask its maker for firmware or instructions.
- If nothing changes:
- it is not that accessory; do not open the case to pull internal drives.
- Evidence to keep:
- what you removed and the result of each start.
Evidence: Bug Check 0x7B INACCESSIBLE_BOOT_DEVICE · Troubleshooting Windows unexpected restarts and stop code errors
- 3
Start in Safe Mode
No special tools
Procedure
- Who:
- you.
- How:
- if Windows ever reaches the desktop, go to Settings, Recovery, Advanced startup, Troubleshoot, Advanced options, Startup Settings, Restart, pick option 4, 5 or 6, then restart normally.
- Result that matters:
- whether the following normal start works.
- If it works:
- Safe Mode loaded the core storage drivers and Windows sees the drive again; watch for a repeat.
- If the blue screen returns:
- the controller and drive still need a check by IT support.
- Evidence to keep:
- time of each attempt and the option you picked.
Evidence: Bug Check 0x7B INACCESSIBLE_BOOT_DEVICE · Troubleshooting Windows unexpected restarts and stop code errors
- 4
System Restore from the recovery options
No special tools
Procedure
- Who:
- you.
- How:
- after automatic repair, on Choose an option, go to Troubleshoot, Advanced options, System Restore and pick a point from before the first crash.
- Result that matters:
- whether a suitable point exists and Windows starts afterwards.
- If it starts:
- the problem came from a software or driver change made after that point.
- If there is no point or it still fails:
- do not keep reinstalling; hand the case to IT support.
- Evidence to keep:
- the date of the restore point used.
Evidence: Bug Check 0x7B INACCESSIBLE_BOOT_DEVICE
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
- 0x0000007B
- 0x7B
- INACCESSIBLE BOOT DEVICE
- STOP 0x0000007B
- stop code INACCESSIBLE_BOOT_DEVICE
What it means
Microsoft defines bug check 0x0000007B as Windows losing access to the system partition during startup. It can come from the boot device driver failing to initialize the disk, a file system that does not recognise the data, repartitioning, a UEFI setting change (such as controller mode) or a new controller, incompatible storage hardware, or a drive that no longer responds. The code does not say which one: only that startup never reached the system volume.
Warnings and stop conditions
- Higheditorial warning
If the repair screen offers to reinstall or format, do not do it without a copy of your files: 0x7B alone does not prove the drive is damaged, and a clean install erases data.
Evidence: Bug Check 0x7B INACCESSIBLE_BOOT_DEVICE
Symptoms and causes
Probable causes · in order
- Recent UEFI or controller changeCommon
If the failure started right after switching the controller from legacy to AHCI, adding a controller or repartitioning, that change is the first suspect and undoing it confirms it.
Evidence: Bug Check 0x7B INACCESSIBLE_BOOT_DEVICE
- New or incompatible drive or controllerPossible
It shows up after adding a drive or storage card, or on a fresh install onto an unsupported controller that needs its own driver at startup.
Evidence: Bug Check 0x7B INACCESSIBLE_BOOT_DEVICE
- Storage device not respondingPossible
If nothing changed and the error repeats, Microsoft says the storage hardware may have failed. Only a manufacturer or technician diagnostic confirms it.
Evidence: Bug Check 0x7B INACCESSIBLE_BOOT_DEVICE · Stop code error or bug check troubleshooting (IT professionals)
Virtual technician
Does INACCESSIBLE_BOOT_DEVICE 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 0x7B INACCESSIBLE_BOOT_DEVICE
Microsoft · 2026 · official_doc
- 2
Stop code error or bug check troubleshooting (IT professionals)
Microsoft · 2026 · official_doc
- 3
Troubleshooting Windows unexpected restarts and stop code errors
Microsoft · 2026 · official_doc
Was this entry useful?