When your PC starts up, a blue screen appears with the message INACCESSIBLE_BOOT_DEVICE and the system restarts repeatedly. Just when you're in the most hurry, Windows decides today's not the day. This blue screen of death (BSOD) indicates a serious boot problem , but in most cases, it can be fixed without losing your data if you stay calm and follow a few logical steps.
This error means that Windows can no longer access the disk or partition from which it should boot . This can happen after a Windows update, a BIOS/UEFI change, a driver failure, file system corruption, or even a physical disk problem. This guide will show you, in an organized and detailed way, what to do to recover the boot process, how to repair the MBR or BCD, what to check in the BIOS, how to proceed on physical and virtual machines, and what options you have if you also need to save your data.
What is the INACCESSIBLE_BOOT_DEVICE error and why does it appear?
The message INACCESSIBLE_BOOT_DEVICE appears on a Blue Screen of Death when Windows cannot properly read the boot device during the startup process. In other words, the system loses communication with the partition where Windows is installed just as it attempts to boot.
This bug became particularly well-known following some problematic Windows 10 updates that, in certain configurations, left the computer stuck in a boot loop with this error. Although less frequent today, it still occurs with Windows 10 and Windows 11, on both traditional HDDs and SSDs.
In many cases, the trigger is a Windows update, a storage controller change, a BIOS/UEFI setting, or the installation of new hardware. But it can also appear after a sudden shutdown, a power outage, or bad sectors on the disk, all of which cause critical boot files (MBR, BCD, winload, etc.) to become corrupted.
In addition to the blue screen itself, it's relatively common to see similar errors such as "BOOTMGR is missing ," "NTLDR is missing," "No bootable device ," or messages indicating that a system file is missing (ntoskrnl.exe, hal.dll, etc.). These usually all stem from the same source: problems with the boot manager or the partition where the system resides.
Most common causes of INACCESSIBLE_BOOT_DEVICE
There could be several culprits behind this blue screen . Knowing them will help you better focus on the solution and avoid wasting time trying to fix it while your PC keeps restarting. The most frequent scenarios are these:
- Storage controllers. They're missing, corrupted, or malfunctioning. We're talking about SATA/AHCI drivers, RAID controllers, NVMe drivers, or even third-party filters that attach to the storage stack. A Windows update can replace a driver with one that's incompatible with your hardware and render your computer unusable.
- Damage to the file system or the boot partition itselfBad sectors on the disk, sudden shutdowns, or malware can cause corruption in the SYSTEM partition or the drive where the Windows folder is located, making it impossible for the system to load the necessary files.
- BIOS/UEFI changes related to storage mode. Switching from IDE to AHCI or RAID, enabling/disabling controllers, changing the boot order, or modifying secure boot options can cause Windows to not recognize the disk as it did when it was installed, generating the INACCESSIBLE_BOOT_DEVICE error.
If you've moved a hard drive with Windows installed to another PC, changed the motherboard, or replaced the hypervisor in a virtual machine, you might also find that the storage controller no longer matches the one used during installation . This difference prevents the system from knowing how to communicate with the drive it's trying to boot from.
First steps: Accessing the Windows Recovery Environment (WinRE)
Before you start trying advanced solutions, you need to enter the Windows Recovery Environment (WinRE) , from where you can use repair options, the command prompt, and other tools.
If the system detects several consecutive failed startups, it will usually display the recovery menu automatically. If not, you can force it :
- Forcing restartsLet the PC display the BSOD and restart; if you manually turn it off or restart it three times in a row while it's trying to boot, Windows usually launches WinRE on the next startup.
- Using an installation USB or DVDBoot from the installation media corresponding to your version of Windows, select your language and on the first screen click on "Repair your computer" instead of "Install now".
Once in WinRE, you'll see several options: Troubleshoot → Advanced options , from where you can access Startup Repair, Command Prompt, System Recovery, Uninstall updates, etc. Almost all the solutions we'll see involve this menu.
Check the disk and boot partition
Before you go crazy with the registry or the BCD, it's a good idea to confirm that the boot disk is present, visible, and in basic good condition . If the hardware doesn't even appear, everything else is useless.
From the WinRE command prompt, run the diskpart tool to view the connected disks:
- Write diskpart and press Enter.
- Run list disk To show all physical disks, check that your system disk is listed as Online and in the size you expect.
- Then run list full To view and locate volumes (partitions):
- The partition with the Windows folder (This will be the drive where the system is installed, usually C: within Windows, although in WinRE it may have a different letter).
- Partition SYSTEM or Reserved for the system, often 100-500 MB FAT32, where the boot manager resides (Bootmgr or the EFI partition).
If you have any doubts about the physical health of your hard drive, it's highly recommended to check its status using tools like CrystalDiskInfo once you've booted up or by connecting it to another computer. If the drive is in a "bad" state or full of reallocated sectors, the problem is very likely due to a hardware failure. Using the Event Viewer to check for storage-related errors is also helpful.
Once you have identified the correct volume, you can run a file system scan with chkdsk to correct logical errors and mark bad sectors:
- At the WinRE command prompt, type chkdsk X: /f /r (replace X: with the letter of the partition where Windows is located).
- Let the process finish; it may take a while if the disk is large or very full.
Automatically repair Windows startup
One of the first things you should try is the built-in Startup Repair option , which analyzes the boot configuration and tries to correct inconsistencies automatically.
To use it , enter the Recovery Environment and follow this path:
- Troubleshoot → Advanced options → Startup Repair.
- Select the Windows installation you want to repair (if you have multiple).
- Wait for the wizard to complete the process and restart to check if the BSOD has disappeared.
This tool can rebuild basic boot files, correct boot paths, and restore certain BCD parameters . It can't always handle everything, but it's non-invasive enough to be worth trying initially.
Repair the boot record: MBR, BCD, and winload
When automatic repair isn't enough, it's time to manually adjust the boot recordThis is where commands like bootrec, bcdedit y bcdbootwhich allow you to fix a corrupt MBR, regenerate the BCD, or recreate the boot files.
From the WinRE command prompt, you can run the basic bootrec sequence :
- bootrec / fixmbr – repairs the master boot record (MBR).
- bootrec / fixboot – writes a new boot sector to the system partition.
- bootrec / RebuildBcd – analyzes Windows installations and rebuilds the BCD store.
If the ` /rebuildbcd` command indicates that it cannot find an installation or returns errors, the BCD store may be severely corrupted. In that case, you can create a backup (if one exists) and rebuild it using `bcdedit` and `bcdboot`.
- Check the BCD with bcdedit pointing to the SYSTEM or EFI partition.
- If the BCD file is present but corrupted, you can export it with bcdedit /export C:\temp\bcdbackup and then adjust specific inputs with bcdedit /set {identifier} option value (for example, changing the boot device).
- If it is completely missing or unusable, resort to bcdboot X:\Windows /s Y: /f ALL (X: is the letter of the partition with Windows, Y: the letter of the SYSTEM or EFI partition) to regenerate all boot files from scratch.
In BIOS/MBR systems, the file Bootmgr It usually resides in the root of the SYSTEM partition (the one that in diskpart (usually called SYSTEM). On UEFI systems, the typical boot manager path is \EFI\Microsoft\Boot\bootmgfw.efiIf these files are missing, bcdboot recreates them if the Windows installation is complete.
Enter safe mode and revert changes
When the error appears right after a major update or driver installation, it's a good idea to try booting into Safe Mode . In this mode, Windows uses a minimal set of drivers and services, which is sometimes enough to repair basic issues or revert changes without triggering the BSOD.
To access safe mode from a Windows system booting into WinRE:
- In WinRE, go to Troubleshoot → Advanced options → Startup settings.
- Press on Restart and, in the subsequent menu, choose the option Enable safe mode (key 4) or safe mode with networking (key 5) if you need the Internet.
- If the system manages to boot, you can uninstall the latest windows update, roll back drivers or restore the system to a previous point.
Often, after booting once in safe mode and restarting normally, if the problem persists , you will need to proceed with more in-depth solutions.
Uninstall problematic updates and pending packages
A common cause of INACCESSIBLE_BOOT_DEVICE is Windows updates that leave the system in an incomplete state : partially installed packages, changes to storage drivers or boot components, etc. In these cases, it's advisable to undo the latest updates and remove any pending packages.
From WinRE you can use the graphical option Uninstall updates within Advanced Options, or go via the command prompt using DISM:
- Run Dism /Image:C: /Get-Packages (replace C: with the drive where Windows is located) to list all installed packages and their dates.
- Locate the latest package associated with a major update.
- Remove it with Dism.exe /Image:C: /remove-package /PackageName:PackageName.
If there are packages in the "Install pending" state that never finish being installed, they can also cause the blue screen. In that case:
- Load the offline software registry branch with:
- reg load HKLM\temp C:\Windows\System32\config\software
- Delete pending session entries in HKLM\temp\Microsoft\Windows\CurrentVersion\Component Based Servicing\SessionsPending.
- Download the hive with reg unload HKLM\temp.
- Move the pending packages to another folder using DISM, after identifying them via Dism.exe /image:C: /get-packages and using /remove-package with a scratchdir temporary.
Additionally, it's recommended to check if the pending.xml file exists in C:\Windows\WinSxS . If it's present, you can rename it to pending.xml.old to force Windows to discard pending operations that never complete.
Update and review storage drivers
Hard drive, SSD, or storage controller drivers are critical pieces of the puzzle. An incompatible, outdated, or broken driver can leave Windows without access to the boot device in a matter of seconds.
Once you manage to boot into safe mode or after temporarily troubleshooting the boot process, go into Device Manager and check the storage sections:
- Right-click on the Start button → Device Manager.
- Unfolds IDE ATA/ATAPI Controllers o Storage controllers.
- Locate the standard SATA AHCI controller (or the manufacturer's specific driver) and use the option Update Driver.
- In the case of Windows 11, also check the NVMe drivers and the SSD firmware.
If you prefer not to do it one by one, you can use third-party tools that automatically search for and update drivers . However, it's advisable to use them judiciously and, if possible, create a restore point before modifying critical drivers.
In virtual machines (Hyper-V, VMware, etc.), this problem can occur when the virtual disk controller type is changed or the VHD/VHDX is migrated to another environment. In these cases, you must ensure that the VM has the correct drivers loaded (IDE, SCSI, Generation 1/2 controller) and that the disk file is properly connected.
Check essential startup services and drivers
In addition to the storage drivers visible in Device Manager, Windows relies on a number of services and drivers marked as critical during startup (Start = 0 in the registry). If any of these are missing, corrupted, or incorrectly configured, you may end up with an INACCESSIBLE_BOOT_DEVICE error.
Working with the offline registry from WinRE, it is possible to review these entries :
- Load the system hive from C: \ Windows \ System32 \ config \ SYSTEM as for example, OfflineSystemHive.
- Query HKEY_LOCAL_MACHINE\OfflineSystemHive\Select to see which ControlSet is active (Default = 1 → ControlSet001, etc.).
- Within that ControlSet, go to Services and checks that keys such as ACPI, DISK, VOLMGR, PARTMGR, VOLSNAP, VOLUME exist, and that their value Start is 0 (load at startup).
- If any are missing, sometimes the entire SYSTEM hive can be restored from RegBack (if there is a copy) replacing the current SYSTEM file with the contents of that folder.
It's also important to check for any suspicious UpperFilters and LowerFilters in storage device classes (for example, under Control\Class\{4D36E96A-E325-11CE-BFC1-08002BE10318} ). If you see third-party filters that don't exist on another healthy machine, you can carefully remove them to prevent them from interfering with the storage stack.
Adjusting the BIOS/UEFI: AHCI mode and active partition
The BIOS or UEFI settings are crucial for Windows to recognize the disk correctly. The INACCESSIBLE_BOOT_DEVICE error can occur if the SATA controller mode has been changed (for example, from IDE to AHCI or RAID) without Windows having the appropriate drivers, or if the boot disk/partition is not correctly selected.
Several users have solved the problem simply by enabling AHCI mode in the BIOS, as it is recommended for modern HDDs and SSDs:
- Turn the device off completely.
- Turn it on and access the BIOS/UEFI by pressing F2, Delete or the key indicated by the manufacturer.
- Look for options Storage o SATA configuration.
- Select the mode AHCI (instead of IDE or RAID), save the changes and restart.
In classic BIOS/MBR systems, it is important that the boot partition is marked as active . If it is not, the computer may display errors such as "No bootable device" or similar.
- With diskpart, select the system disk: salt disk 0 (for example).
- List the partitions with list partition and select the startup one: sel partition 1 (the one containing \\Boot or the one reserved for the system).
- Run active to mark it as the active partition and confirm with detail partition.
In Azure virtual machines or other environments, this type of problem is solved by connecting the disk to a recovery machine , adjusting the active partition and repairing the BCD with bcdboot , and then reattaching it to the original VM.
Scan the system for malware
It's not the most common thing, but it's not impossible either: certain types of malware can touch boot files, drivers, or the file system and end up triggering an INACCESSIBLE_BOOT_DEVICE error after an update or a reboot.
Windows includes Microsoft Defender by default, which today offers a level of protection similar to many commercial antivirus programs. Once you manage to boot the system (even in safe mode), perform a full system scan:
- Open Windows Security (Defender).
- Go to Antivirus and threat protection.
- Choose Complete analisis instead of the fast one.
- Let it finish, even if it takes several hours.
If you prefer, you can use specialized anti-malware tools, always downloaded from official sources, to ensure that there is no malicious software acting as the trigger for the boot failure.
Repair Windows 11 and Windows 10 when nothing else works
When you've tried Startup Repair, chkdsk, bootrec, bcdboot, safe mode, uninstalling updates and adjusting BIOS/UEFI, and the computer still won't boot, it's time to consider more drastic measures to restore the integrity of Windows.
In Windows 11 and Windows 10 you have several final cards :
- System RestoreIf you had restore points enabled, you can revert to a state prior to the problem from System recovery in WinRE. This reverts drivers, updates, and registry changes.
- Reset this PCFrom Settings → System → Recovery (if you can boot) or from WinRE, you can start a reset process, choosing to keep personal files or delete everything.
- clean reinstallBoot from an installation USB drive, format the system partition, and install Windows from scratch. This is the most drastic option, but it also leaves the cleanest environment.
If you choose to reset or reinstall and you can still access the drives, it's best to first make a full backup of your data to another drive. If the system won't boot under any circumstances, you can remove the drive and connect it to another PC, or use recovery software that boots from an external drive.
The INACCESSIBLE_BOOT_DEVICE error is alarming, but it's almost always due to a combination of driver issues, boot configuration problems, and file corruption that can be addressed calmly: checking the correct disk and partition, repairing the MBR and BCD, uninstalling conflicting updates, adjusting BIOS/UEFI settings, and reviewing critical drivers. If you still can't get the system to boot, it's possible to recover your data with recovery tools and restore your computer to like-new condition with a clean Windows reinstallation.
