INACCESSIBLE_BOOT_DEVICE 0x0000007B after a BIOS or clone change

Fix it now

0x0000007B means Windows lost access to the system partition during startup. Microsoft’s documented causes include changing the BIOS configuration, installing a disk controller, and an unsupported controller that needs other drivers present when Windows starts – which is why a firmware setting change is usually what did it.

diskpart
list disk
list vol
exit

1. Think about what changed. A firmware update or reset, a storage mode change, a clone onto different hardware, or a new drive fitted immediately before the failure is almost always the cause.
2. Enter firmware setup and look at the storage configuration. If the mode has changed – most obviously to or from a vendor RAID or volume-management option – put it back to what the machine was installed with and start again.
3. Confirm the disk is listed in firmware setup at all. If it is not, this is a cabling, module or drive fault rather than a driver one.
4. If the disk is present but Windows still will not start, boot the recovery environment and run the commands above. list disk should show the OS disk Online, and list vol should show the Windows and system volumes Healthy.
5. If the storage mode has to stay changed, inject the matching driver into the offline installation: Dism /Image:<OSdrive>:\Windows /Add-Driver /Driver:<folder holding the extracted .inf files> /Recurse, using the letters list vol reported.

Point DISM at extracted driver files, not at an installer package. Dism /Image:<OSdrive>:\Windows /Get-Drivers afterwards confirms what is now in the image.

If the machine starts and stays started, stop here. The next section explains why a firmware toggle stops a working installation and what to check when the mode is not the problem.

Why it happens

Windows does not load all of its drivers at startup. A small set is marked to start at boot, and among them are the drivers that can reach the disk holding Windows. Everything else – including alternative storage drivers – is loaded later, from that same disk. So the boot-start storage driver has to match the controller the firmware is presenting, or there is nothing to read the rest of the system with.

That is what makes a firmware toggle so effective at breaking a working installation. Microsoft’s own cause list for this code includes configuration changes such as repartitioning the system partition, changing the BIOS configuration or installing a disk controller, and separately notes that the system might have been installed on an unsupported disk controller, because some disk controllers require other drivers to be present when Windows starts. Change the mode and the machine presents a different controller; the driver that was loaded no longer recognises anything, and the one that would is either absent or not configured to start at boot.

The same reasoning covers the clone case. An installation captured from one machine and restored onto another has never had the target machine’s storage driver installed, so there is nothing marked boot-start that can see the disk. And it covers the update case: a pending or partly applied update can leave the boot-critical driver set inconsistent, which is why Microsoft’s troubleshooting for this code has a whole section on reverting pending actions.

0x0000006B is often filed alongside this one, and it deserves its own reading. PROCESS1_INITIALIZATION_FAILED means the initialisation of Windows failed, with parameter 1 carrying the NT status code that caused it. Microsoft’s cause list is broader than storage: any part of the disk subsystem including bad disks, bad or incorrect cables, mixing different ATA-type devices on one chain and drives unavailable because of hardware regeneration – but also a missing file from the boot partition, or a driver a user accidentally disabled on the Drivers tab. Read parameter 1 before assuming which.

Full reference

What changed, and what to do about it

The recovery environment sequence Microsoft documents

1. diskpart, then list disk – the OS disk should be Online with its size shown.
2. list vol – the Windows RE, Windows and system volumes should all be present and Healthy.
3. bcdedit – the boot manager and boot loader entries should point at the right device, path, osdevice and systemroot; UEFI machines show .efi paths.
4. Dism /Image:<OSdrive>: /Get-Packages for pending update packages, then dism /Image:<OSdrive>:\ /Cleanup-Image /RevertPendingActions if any are stuck.
5. The offline SYSTEM hive for boot-critical service Start values and for non-Microsoft storage filters.
6. chkdsk /f /r <OSdrive>: and sfc /scannow /offbootdir=<OSdrive>:\ /offwindir=<OSdrive>:\Windows to check the file system and the system files.
7. Bcdboot <OSdrive>:\windows /s <SYSTEMdrive>: /f ALL to rewrite the boot files if the store itself is the problem.

Injecting a storage driver offline

/Recurse is convenient and easy to overuse: driver packages that contain several .inf files sharing payload files are expanded into separate folders with their own copies. Point it at the storage driver you need rather than at a whole downloads folder.

The codes you may see instead

Microsoft’s resolution list for a machine that does start

• Boot to Safe Mode and then boot normally.
• Use the scan disk utility to check for file system errors.
• Run a virus detection program.
• Confirm there is sufficient free space on the drive.
• Check Device Manager for devices marked with an exclamation point, and the System log in Event Viewer.
• Run the hardware diagnostics the system manufacturer supplies.
• Use SFC /scannow, and System Restore to return to an earlier restore point.

When the disk is not detected at all

Everything above assumes the machine can see the drive. If firmware setup does not list it, or lists it intermittently, none of the driver work applies. Reseat data and power cables at both ends, or reseat the M.2 module and check its retention screw; try a different port and a known-good cable; and confirm across several cold starts rather than one. A drive that appears once in five attempts is failing, and the right next step is imaging it rather than repairing the installation on it.

Every code this article covers

Confirm the fix worked

1. The machine starts to the desktop on three consecutive cold starts.
2. Device Manager lists the storage controller in use without a warning icon.
3. Disk Management shows the disk at the expected capacity with no volume marked unhealthy.
4. The machine still starts after the full vendor driver package is installed over the injected driver.
5. Dism /Image:<OSdrive>:\Windows /Get-Drivers is no longer needed – the driver is present in the running system, visible in Device Manager.

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