ACPI BIOS Error (0x000000A5): Causes, and Step-by-Step Solutions (2026 Guide)

The ACPI BIOS Error is a frustrating Blue Screen of Death (BSOD) that can stop your computer from booting or even prevent Windows from installing. If you’re seeing the ACPI_BIOS_ERROR (0xA5), don’t worry; this guide walks you through why it happens and how to fix it step by step.

What Is ACPI BIOS Error & Its Causes

ACPI (Advanced Configuration and Power Interface) is responsible for managing:

• Power states (sleep, hibernation)
• Hardware resource allocation
• CPU and device control

The ACPI error typically occurs during:

• System startup
• Windows installation
• After a Windows update or upgrade
• Waking from sleep or hibernation

The most common error code is ACPI_BIOS_ERROR (0x000000A5), which usually indicates that Windows cannot properly communicate with the BIOS/UEFI firmware through the ACPI (power management interface).

Before jumping into fixes, it’s important to understand the root of the problem. The ACPI BIOS error on Windows 11/10/8/7 is usually caused by:

• Outdated or incompatible BIOS firmware
• Corrupted or misconfigured ACPI tables
• Driver conflicts (especially chipset and storage drivers)
• Incorrect BIOS settings (AHCI, power settings)
• Hardware incompatibility/changes (SSD, RAM, motherboard)

How to Fix ACPI BIOS Error (Step-by-Step Solutions)

Below are the most effective solutions to fix ACPI error. First, you can try unplugging all USB devices, external hard drives, and printers, as faulty hardware can trigger this error. You also need to ensure that the RAM sticks are properly seated and that the motherboard is not shorting out against the case.

Solution 1: Update BIOS (Most Effective)

Updating the BIOS ensures your system firmware is compatible with the latest Windows ACPI requirements. This is the most reliable fix, especially after system upgrades or hardware changes.

Step 1. Press Win + R, type msinfo32, and press Enter.

Step 2. Check your current BIOS Version/Date.

Step 3. Go to your motherboard or PC manufacturer’s website.

Step 4. Download the latest BIOS version.

Step 5. Copy the BIOS file to a USB drive.

Step 6. Restart your PC and enter BIOS (press F2/DEL/Esc at startup).

Step 7. Open the BIOS Update Utility.

Step 8. Select the BIOS file and start the update.

How to Update Gigabyte BIOS (2026 Guide for Safe Flashing)

Solution 2. Reset BIOS to Default Settings

Incorrect BIOS configurations or overclocking settings can trigger ACPI errors. Resetting to default eliminates these conflicts.

Step 1. Restart your PC and repeatedly press the setup key (usually F2, F10, F12, Esc, or Delete) before Windows boots.

Step 2. Look for a menu option labeled “Load Setup Defaults”, “Load Optimized Defaults”, or “Reset to Default”.

Step 3. Select the option, confirm when prompted, and choose “Save and Exit” (usually F10).

Solution 3. Change SATA Mode

Incompatibility between storage modes and system drivers can cause ACPI BIOS errors, especially during Windows installation or after SSD upgrades.

Step 1. Turn on your computer and press the BIOS key (F2, F12, Del, or Esc).

Step 2. Go to the Advanced, Integrated Peripherals, or Storage Configuration menu.

Step 3. Select the SATA Controller Mode, Configure SATA as, or similar setting, and change it from AHCI/RAID to IDE or Compatibility.

Step 4. Select “Save Changes and Exit” (often F10) to apply the changes and restart.

Solution 4. Modify ACPI Suspend Type

Incorrect power state settings in BIOS can interfere with ACPI functionality, especially during sleep/wake cycles.

Step 1. Reboot your computer, then immediately press the key (usually F2, F12, Delete, or Esc) during startup to enter the setup utility.

Step 2. Navigate to the “Power”, “Power Management”, or “Advanced” tab.

Step 3. Locate the setting named “ACPI Suspend Type,” “Sleep State,” or similar. Change the setting from S3 or Auto to S1 (often listed as S1/POS or “Power on Suspend”).

Step 4. Select “Save and Exit” to apply changes and reboot.

Solution 5. Update Chipset and System Drivers

Chipset drivers control communication between the OS and hardware. Outdated drivers can break ACPI functionality.

Step 1. Open Device Manager (Win+X).

Step 2. Expand System Devices.

Step 3. Right-click your chipset component and select Update driver.

Step 4. Restart your PC.

Solution 6. Uninstall Microsoft ACPI‑Compliant Driver

The Microsoft ACPI-Compliant Driver is a crucial Windows component that acts as the bridge between the computer hardware’s firmware (BIOS) and the OS, managing power and PnP devices. Some users report successfully fixing the ACPI BIOS error by uninstalling this driver.

Step 1. Right‑click the Start menu and select Device Manager.

Step 2. Expand the Batteries option.

Step 3. Locate the driver named Microsoft ACPI‑Compliant Control Method Battery or similar.

Step 4. Right‑click it and select Uninstall device.

Step 5. Restart your computer. The system will automatically reinstall the driver.

Solution 7. Run Startup Repair

If your system cannot boot, Startup Repair can automatically fix boot-related issues linked to ACPI errors.

Step 1. Boot from a Windows installation USB.

Step 2. Click Repair your computer.

Step 3. Go to Troubleshoot → Advanced Options.

Step 4. Select Startup Repair.

If your PC boots, you can access Startup Repair via Settings.

Step 1. Open Settings. (press Win + I).

Step 2. Go to Update & Security (Windows 10) or System (Windows 11).

Step 3. Select the Recovery tab on the left.

Step 4. Under the Advanced Startup section, click Restart now.

Step 5. Your PC will restart into the blue “Choose an option” screen. From there, navigate to Troubleshoot > Advanced Options > Startup Repair.

Solution 8. Perform System Restore

If the error started after an update or software installation, restoring your system to a previous state can resolve the issue.

For a working PC:

Step 1. Click the Start button, type “Create a restore point,” and open System Properties.

Step 2. In the System Protection tab, click the System Restore… button.

The System Restore wizard will open. Click Next to proceed.

Step 3. You’ll see a list of available restore points. Select one that was created before you started experiencing the problem.

Step 4. Confirm your choices on the final screen and click Finish. Your PC will restart and begin the restoration process.

For a PC that can’t boot:

If you can’t get to your desktop, you can access System Restore from the Windows Recovery Environment (WinRE).

Step 1. Boot into WinRE: Turn on your PC. When the Windows logo appears, press and hold the Power button for 5-10 seconds to force a shutdown. Repeat this 2-3 times, and Windows will eventually boot into the “Automatic Repair” screen. From there, click Advanced options.

Step 2. Navigate to System Restore: At the “Choose an option” screen, go to Troubleshoot > Advanced Options > System Restore.

Step 3. The System Restore wizard will launch. Follow the on-screen instructions to choose a restore point and complete the process.

What to Do If You Encounter ACPI BIOS Error During Windows Installation?

If you encounter the ACPI BIOS error while installing Windows, try the following 2 methods:

Method 1: Press F7 to disable ACPI mode

During installation, when prompted to load storage drivers, press the F7 key. The system will not notify you that F7 was pressed, but this silently disables ACPI mode, allowing you to continue the installation.

Method 2: Enter Safe Mode

If your computer is stuck in a restart loop, try entering Safe Mode:

Step 1. Restart your computer. During startup, press F8 repeatedly (or press the power button three times) to enter the system recovery interface.

Step 2. Navigate to Troubleshoot → Advanced Options → Startup Settings → Enable Safe Mode with Networking.

If you can enter Safe Mode, the main system is likely intact, and the problem is most likely driver‑related.

Conclusion

The ACPI BIOS error is a common but solvable blue screen problem, usually caused by outdated drivers, incorrect BIOS configuration, or hardware compatibility issues. Follow the 8 fixes in this article from simplest to most complex, and in most cases, you will successfully resolve the problem. If none of the methods work, contact your computer manufacturer’s technical support for further assistance.

Hope this article helps!