INACCESSIBLE_BOOT_DEVICE during upgrade to Windows 11

glasskuter said:

Welcome to the forum.
Please post a screenshot of disk management.

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Clean Install Windows 11

This tutorial will show you step by step on how to clean install Windows 11 at boot on your PC with or without an Internet connection and setup with a local account or Microsoft account. Windows 11 has all the power and security of Windows 10 with a redesigned and refreshed look. It also comes...

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• Choose Repair your computer → Troubleshoot → Startup Repair. Let it scan and attempt automatic fixes.

glasskuter said:

That DM looks normal. Here are the things I know can cause such a problem. It could be any one of them but I'm leaning toward it being #1.

1. An upgrade rewrites the BCD data (no matter if the upgrade is performed by windows update, the installation assistant, or you). BCD is your bootloader.

2. I also know that the 11th gen i5 requires access to the proper storage controller drivers if RAID or VMD is enabled in the bios. Those drivers are called Intel Rapid Storage Controller.

3. I also read that if one goes into an upgrade with Bitlocker or Drive Encryption enabled that it can cause problems.
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Personally, if it were me, I would back up my personal data (unless you use a MS account and are syncing documents, desktop, pictures, and videos to Ondrive. In that case your files should be preserved) and do a clean install. I would change my disk mode in UEFI bios to AHCI with no RAID or VMD. Then boot from the installation usb drive. Doing so will make the Windows 11 install media SEE your drive.

Otherwise you will have to download the IRST driver package from Acer for your device, unzip the package and copy the drivers to another usb drive. Start the install process with both usb drives connected. During the install process you insert the drivers during the step when you see "add driver" Then the install will continue. Changing the bios setting is so much easier and less messy.

Clean Install Windows 11

This tutorial will show you step by step on how to clean install Windows 11 at boot on your PC with or without an Internet connection and setup with a local account or Microsoft account. Windows 11 has all the power and security of Windows 10 with a redesigned and refreshed look. It also comes...

www.elevenforum.com

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That said, if you're absolutely determined you can perform the upgrade again & try to fix the problem if boot fails again. You will need a Windows 11 install usb drive to perform these steps.

Before starting the upgrade, Disable Bootlocker or Device Encryption in Windows 10 first. If the upgrade completes and it does not boot, try these fixes one at a time, trying to boot after each one. If it is not fixed, keep booting from the install disk to try the next possible fix.
NOTE: You will have to have already downloaded the drivers needed for step 3.
Go to Acer and download the Intel Rapid Storage Controller driver package for your device .Unzip it and copy the drivers to a flash drive

Fix 1. Insert a Windows 11 install usb and boot from it.

• Choose Repair your computer → Troubleshoot → Startup Repair. Let it scan and attempt automatic fixes.

Fix 2. Repair the BCD

From the recovery environment:

Open command prompt, type one at a time
bootrec /fixmbr
bootrec /fixboot
bootrec /scanos
bootrec /rebuildbcd

Fix 3. Load missing storage controller drivers using DISM.

From recovery, open Command Prompt and type:
dism /image:C:\ /add-driver /driver:D:\Drivers\iaStorAC.inf
(spaces after C:\ and after add-driver)
(Replace D:\Drivers\Drivername with the actual full path to the driver on the usb)

There are a number of drivers in the IRST driver package so do that for each one.
If anyone sees any mistakes in these commands, please let me know, I've only done this once.


Good Luck.

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glasskuter said:

Open command prompt, type one at a time
bootrec /fixmbr
bootrec /fixboot
bootrec /scanos
bootrec /rebuildbcd

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• Updates the boot code on MBR-style disks by writing new boot code to the MBR and/or Volume Boot Records (VBRs).
• Not applicable to GPT disks, since GPT uses the EFI System Partition (ESP) with EFI boot files, not MBR/VBR boot code.

• Writes a standard Windows MBR to the first sector of the disk (sector 0).
• Only relevant for MBR disks; GPT disks don’t use an MBR for booting (they just have a “protective MBR” to prevent legacy tools from misidentifying the disk).

• Writes a new boot sector (VBR) to the system partition.
• Only meaningful on BIOS/MBR setups; UEFI/GPT systems use the EFI System Partition (ESP) instead of a boot sector.
• In Windows 10 (version 1709 and later) and Windows 11, the bootrec /fixboot command no longer works in the Windows Recovery Environment (WinRE), regardless of whether the disk uses GPT or MBR. Running the command results in an "Access is denied" error.

• Scans all disks for Windows installations that are not in the BCD store (Boot Configuration Data).
• It only reports what it finds — it does not add them to the BCD store automatically.

• Scans all disks for Windows installations that are not in the BCD store.
• It then gives you the option to add them into the BCD store.

• bootrec /rebuildbcd only manipulates the BCD database itself.
• It does not recreate the actual boot files (like bootmgfw.efi or bootmgr) — that’s what the bcdboot command does.
• If the system partition’s boot files are missing or corrupted, bootrec /rebuildbcd alone won’t fix that.

MBR Windows 10 > to UEFI only computer - Windows 10 Help Forums

Hi everyone, I've tried diff approaches but can't find the solution. Source computer: my daily driver, has both UEFI and legacy compatibility. Because of personal preference I installed Windows 10 Pro in legacy / MBR mode using one single partition, becau

www.tenforums.com

Rheinvalor001 said:

Hey guys, may I ask for help

This happened during Windows 11 Installation (I used the Installation Assistant to upgrade) and I’ve faced this error, when my device restarted it shows the error INACCESSIBLE_BOOT_DEVICE, i tried disabling VMD on my BIOS,

But it unsuccessfully installed Windows 11, leading me to undoing system changes, now it went back to Windows 10, unable to boot, tried opening the VMD on again and boots normally

What should I do when I’m upgrading to Windows 11? To prevent this from happening.

P.S. I want to try and upgrade through Windows Update, but i’m fearing that the error may show up again…

Thanks!

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1. Insert the Media (DVD/USB) in your PC and restart.
2. Boot from the media.
3. Select Repair Your Computer.

1. Choose Command Prompt from the menu:

Thorenzz said:

Boot from Windows 11 Installation Media:

1. Insert the Media (DVD/USB) in your PC and restart.
2. Boot from the media.
3. Select Repair Your Computer.

Select Troubleshoot.

1. Choose Command Prompt from the menu:

Type in the command:
Diskpart

Type in the command:
List disk (Note which disk is your Boot drive number mine is 0)

Type in the command:
Sel disk 0

Type in the command:
List vol (Note which volume is the EFI partition mine is 4, usually 100MB or 200MB partition without assigned letter)

Type in the command:
Sel vol 4

Type in the command:
assign letter=V:

Type in the command:
Exit

Type in the command:
V:

After you have assigned a drive letter Using Diskpart You can format the EFI partition:
Example: if you assigned a letter V to the partition the command would be:

format V: /FS:FAT32

Type in the command:
bcdboot C:\windows /s V: /f UEFI

Let us know if this work. In most cases this fixed any UEFI BCD issues for me.

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