What is acpi.sys?
The file acpi.sys is a Windows device driver file located in %SYSTEMROOT%:\WINDOWS\System32\DriverStore\FileRepository\acpi.inf_amd64_neutral_2a841284c9de8962\. Its file size is 334416 bytes, the version is 6.1.7600.16385 and the last update is on 7/13/2009 4:19:35 PM.

The acpi.sys is used to support your Windows hardware device driver ACPI Driver for NT. If the driver ACPI Driver for NT becomes corrupted or outdated, you would receive acpi.sys blue screen of death (BSOD), sometimes along with error code 0x1365(Logon restriction) and stop error messages 0X8955586M. Even you start your computer in Safe Mode, you would get system restart loop problems.

How to fix acpi.sys BSOD?
The easiest way to resolve acpi.sys BSOD issue is to download and update your device driver ACPI Driver for NT and keep it the latest.

To download and update acpi.sys driver, you can use acpi.sys file repair tool Driver Mechanic.

Driver Mechanic helps download and update your acpi.sys driver to repair acpi.sys problems.

Driver Mechanic: Downloads and Updates acpi.sys Device Drivers Automatically!