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0x000000A5ACPI_BIOS_ERRORStop codeWidely reported

ACPI_BIOS_ERROR (0x000000A5): what it means and how to fix it

Updated Oct 23, 2026 · Checked against Microsoft documentation · How this page is made

Quick answer

This error means your computer's BIOS is not fully compatible with the power management standards Windows expects. It is most commonly caused by outdated BIOS firmware or incorrect power settings. The first thing to try is updating your motherboard BIOS to the latest version.

What it means

Understanding the ACPI_BIOS_ERROR

When you see the ACPI_BIOS_ERROR, it means that Windows has encountered a problem while communicating with your computer's BIOS regarding power management and hardware configuration. ACPI stands for Advanced Configuration and Power Interface. It is the set of rules that allows your operating system to control hardware power states, such as putting your computer to sleep, waking it up, or managing battery usage.

Your BIOS acts as the bridge between your hardware and Windows. If this bridge provides information that is incomplete, formatted incorrectly, or simply does not follow the standard rules, Windows cannot safely manage your hardware. To prevent potential data loss or hardware damage, Windows stops the system immediately and displays this blue screen.

Why it happens

This error is almost always a sign that the firmware on your motherboard is not communicating correctly with the version of Windows you are running. This can happen if you have recently installed new hardware that the current BIOS version does not fully understand, or if the BIOS settings themselves are configured in a way that conflicts with Windows power management requirements. In some cases, it may occur during a fresh installation of Windows if the installer detects that the motherboard's power management tables are not compliant with the Windows specification.

Common causes

  • Outdated motherboard BIOS firmware.
  • Incorrect power management settings in the BIOS.
  • Hardware components that are not fully compatible with ACPI standards.
  • Corrupted or misconfigured system boot settings.

How to fix it

Safest and most likely fixes first. Readers' answers to "Did this fix it?" reorder this list over time.

  1. Update your motherboard BIOS

    This is the most effective solution if your hardware is relatively new or if you have recently added new components.

    1. Visit the official support website for your motherboard or computer manufacturer.
    2. Search for your specific model to find the latest BIOS or UEFI firmware update.
    3. Follow the manufacturer's instructions carefully to install the update.
    4. Restart your computer once the update process is complete.
    Did this fix it?

  2. Reset BIOS settings to default

    Use this if you have recently changed power-related settings in your BIOS and the error started appearing afterward.

    1. Restart your computer and repeatedly press the key specified on the screen to enter the BIOS or UEFI setup menu.
    2. Look for an option labeled Load Setup Defaults, Restore Defaults, or similar.
    3. Select this option and confirm your choice.
    4. Save your changes and exit the BIOS menu to restart your computer.
    Did this fix it?

  3. Check for recent hardware changes

    Use this if the error began immediately after installing new internal hardware.

    1. Power off your computer and unplug it from the wall outlet.
    2. Remove any recently added hardware components.
    3. Attempt to start the computer to see if the error persists.
    4. If the system boots normally, the removed hardware may be incompatible with your current BIOS version.
    Did this fix it?

Is it just you?

25+ Microsoft Q&A threads discuss this, 1 active in the last 30 days. Most recent activity:

Checked Oct 23, 2026. Refreshed automatically every few days.

Sources

Frequently asked questions

Can I fix an ACPI_BIOS_ERROR without losing my files?

Yes, this error is related to communication between your hardware and the operating system, not your personal data. Updating your BIOS or adjusting settings will not delete your files.

Does this error mean my motherboard is broken?

Not necessarily. It usually means the motherboard firmware is outdated or configured incorrectly, rather than the hardware itself being physically damaged.

Why does this happen during a Windows installation?

The Windows installer checks your motherboard's power management tables before proceeding. If it finds that your BIOS does not comply with the required standards, it will stop the installation to prevent system instability.

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