What is ACPI?
The genuine ACPI.sys file is a software component of Microsoft Windows Operating System by Microsoft Corporation.
"ACPI.sys", when located in "C:\Windows\System32\drivers", is Microsoft's Advanced Configuration and Power Interface (ACPI) driver. It is a crucial component of the Windows Operating System's implementation of the ACPI open standard which gives control of computer and device power management and plug and play (PnP) device enumeration to the kernel operating system instead of being on a firmware level. Its device-specific interaction with the functional drivers of ACPI-compliant devices connected to the system is driven by the manufacturer's ACPI Machine Language (AML) specifications loaded from the ACPI BIOS into each device's operational region in memory, where ACPI.sys interprets them.
ACPI stands for Windows Advanced Configuration and Power Interface Driver
ACPI.sys is a Windows driver. A driver is a small software program that allows your computer to communicate with hardware or connected devices. This means that a driver has direct access to the internals of the operating system, hardware etc.
The free file information forum can help you determine if ACPI.sys is a Windows system file or if it belongs to an application that you can trust.
Run a free scan to check for ACPI drivers in need of updating
Since 2005, file.net has researched facts about Windows processes and files, analyzed user experiences, and examined files using its own analysis tools. Around 10,000 users rely on it every day.
ACPI.sys file information
The process known as ACPI Driver for NT or Microsoft ACPI Driver belongs to software Microsoft Windows Operating System or Operativsystemet Microsoft Windows by Microsoft (www.microsoft.com).
Description: The original ACPI.sys is an important part of Windows and rarely causes problems. ACPI.sys is located in the C:\Windows\System32\drivers folder.
Known file sizes on Windows 10/11/7 are 187,776 bytes (62% of all occurrences), 274,304 bytes, 274,624 bytes or 265,688 bytes. 
The driver can be started or stopped from Services in the Control Panel or by other programs.
The program has no visible window. The service has no detailed description. The ACPI.sys file is a Microsoft signed file.
ACPI.sys appears to be a compressed file.
Therefore the technical security rating is 3% dangerous; however you should also read the user reviews.
Recommended: Identify ACPI.sys related errors
Important: Some malware disguises itself as ACPI.sys, particularly when not located in the C:\Windows\System32\drivers folder. Therefore, you should check the ACPI.sys process on your PC to see if it is a threat. We recommend Security Task Manager for verifying your computer's security. This was one of the Top Download Picks of The Washington Post and PC World.
Best practices for resolving ACPI issues
A clean and tidy computer is the key requirement for avoiding problems with ACPI. This means running a scan for malware, cleaning your hard drive using 1cleanmgr and 2sfc /scannow, 3uninstalling programs that you no longer need, checking for Autostart programs (using 4msconfig) and enabling Windows' 5Automatic Update. Always remember to perform periodic backups, or at least to set restore points.
Should you experience an actual problem, try to recall the last thing you did, or the last thing you installed before the problem appeared for the first time. Use the 6resmon command to identify the processes that are causing your problem. Even for serious problems, rather than reinstalling Windows, you are better off repairing of your installation or executing the 7DISM.exe /Online /Cleanup-image /Restorehealth command. This allows you to repair the operating system without losing data.
To get your computer running as fast as it did on day one, you can 8reset your PC. Your personal files will remain intact, but any programs you installed will need to be reinstalled.
To help you analyze the ACPI.sys process on your computer, the following programs have proven to be helpful: ASecurity Task Manager displays all running Windows tasks, including embedded hidden processes, such as keyboard and browser monitoring or Autostart entries. A unique security risk rating indicates the likelihood of the process being potential spyware, malware or a Trojan. A good Bantivirus software detects and removes sleeping spyware, adware, Trojans, keyloggers, malware and trackers from your hard drive.
Other processes
downloader.dll genius.exe wallpaper64.exe ACPI.sys discordptb.exe tinybho.dll cdloader2.exe tomcat6.exe qipguard.exe bdntwrk.exe mirkatservice.exe [all]
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Summary: Average user rating of ACPI.sys: based on 22 votes with 16 user comments. 13 users think ACPI.sys is essential for Windows or an installed application. 5 users think it's probably harmless. One user thinks it's neither essential nor dangerous. 3 users think ACPI.sys is dangerous and recommend removing it. 6 users don't grade ACPI.sys ("not sure about it").