Today one of my colleagues triggered a Windows 11 feature update on a VM. The result was a Windows 11 VM that would no longer start. The error is actually a well-known problem inaccessible bootdeviceand has often fixed with the following instructions https://nerdschalk.com/stop-code-inaccessible-boot-device-on-windows-11-17-fixes-and-5-checks-to-do But in this case none of the 17 tips and tricks were successful 😑

When I tried the tips, I quickly realized that the hard drive with the Windows installation was not recognized by the recovery system at all. Commands such as diskpart list disk or diskpart list vol returned no disk/no volume. This meant that every tip did not work because the commands do not see the defect Windows Installation 🙄.

First we have to make sure that the recovery system sees the broken Windows installation. We do this by loading a driver in the recovery. We use proxmox and the Controller with the Disk is virtio. Inserting the virtio ISO with the Drivers in CD-ROM (Letter E)

pnputil -a e:\vioscsi\w11\amd64\vioscsi.inf -i

or

pnputil -a e:\viostor\w11\amd64\viostor.inf -i

after this command the defect Windows Installation is accessible with Driver letter C

Now the tips worked at least partially, but none of them fixed the error. The Commands for loading the Driver is not persistent. So if you load a driver with pnputil it is active as long you did not reboot. Fortunately, I could still remember the days of Windows Images and Dism. I couldn't remember the exact command, but at least I had the right keywords to search for.

https://learn.microsoft.com/en-us/windows-hardware/manufacture/desktop/add-and-remove-drivers-to-an-offline-windows-image?view=windows-11 has the Infos for building the right Command.

Dism /Image:c: /Add-Driver /Driver:e:\vioscsi\w11\amd64\vioscsi.inf

Everything else is not worth mentioning. an exit and subsequent restart and Windows can be started again 😎