Windows Update: Start aborts with ACPI.sys error message

After installing the Windows updates from the May Patchday, Windows 11 23H2 and 22H2 may experience startup problems. In addition to a few physical devices, virtual machines are particularly affected. An unplanned update corrects the underlying error.

As Microsoft explains in the Windows Release Health Notes, affected devices show the following error message:

"Your PC/Device needs to be repaired
The operating system couldn't be loaded because a required file is missing or contains errors.
File: ACPI.sys
Error code: 0xc0000098"

Although some physical devices are affected, the error primarily occurred on devices in virtual environments: On Azure Virtual Machines, Azure Virtual Desktops and virtual machines on dedicated servers using Citrix or Hyper-V. Windows Home and Pro users are therefore probably rarely affected by the problem.

Other file names also possible

The ACPI.sys (Advanced Configuration and Power Interface) driver is a critical Windows system driver with which Windows can manage hardware resources and power-saving statuses. However, the error messages on systems that do not start can also display other file names, Microsoft adds.

Microsoft has released the KB5062170 update outside the usual series. It upgrades the Windows 11 versions to build numbers 22621.5415 and 22631.5415 respectively. It is already in line with the May update previews and adds the solution to the issue of systems not starting with the recovery error. However, there is no automatic update. Affected admins must download and install the update manually from the Windows Update Catalog.

Microsoft also provides brief instructions in the Windows Release Health Notes on how to restore affected devices if Windows cannot be started. To do this, admins should start the Windows Recovery Environment (WinRE) if possible. On machines that do not have WinRE activated, however, they should mount the virtual hard disk (vhd) from another device, mount the VHD in another VM or device as a data drive, and finally bring it back to the affected VM. Then restart Windows in normal mode. This should reset Windows to the status of the last Windows update installed. Affected Azure customers should follow more detailed instructions from Microsoft on how to restore.

In mid-April, Microsoft acknowledged problems with Windows updates on Patchday. At that time, domain controllers had problems in the network and Windows 11 desktops could crash. Last week, Microsoft also distributed unplanned updates that resolved issues with BitLocker and Hyper-V on numerous operating system versions from Server to Desktop.

(dmk)