How to fix error 0x000000a5 in Windows 11

Solution Steps

1. 1 Press Windows key + I to open Settings. Go to System → Recovery → Advanced startup and click 'Restart now'. This will boot into the Windows Recovery Environment, where you can access advanced troubleshooting tools. This step is essential because the error may prevent normal boot, and Advanced Startup Options allow you to fix the system without a full boot.
2. 2 In the Advanced Startup Options, select Troubleshoot → Advanced options → Startup Settings, then click Restart. After the restart, press 4 or F4 to enable Safe Mode. Safe Mode loads Windows with minimal drivers and services, which can help you bypass the problematic ACPI driver and allow you to make changes.
3. 3 Once in Safe Mode, press Windows key + X and select 'Device Manager'. Expand 'System devices' and look for 'ACPI Fixed Feature Button' or similar ACPI entries. Right-click each ACPI device and select 'Update driver' → 'Search automatically for drivers'. This ensures Windows has the latest compatible ACPI drivers, which may resolve the communication issue.
4. 4 If updating drivers doesn't help, you need to update your BIOS. Visit your motherboard or computer manufacturer's website (e.g., Dell, HP, ASUS) and find the support/downloads page for your exact model. Download the latest BIOS update file and follow the manufacturer's instructions to flash it. This is often done via a USB drive or a Windows-based utility. Updating BIOS can add support for newer Windows versions and fix ACPI bugs.
5. 5 If the error persists, you may need to reset BIOS settings to default. Restart your computer and press the key to enter BIOS setup (usually Del, F2, or F10). Look for an option like 'Load Optimized Defaults' or 'Reset to Default' and confirm. Save and exit. This clears any incorrect ACPI settings that might be causing the crash.
6. 6 As a last resort, you can disable ACPI in the BIOS, but this is not recommended as it can cause other issues. Instead, consider using the Windows Memory Diagnostic tool: press Windows key + R, type 'mdsched.exe', and press Enter. Choose 'Restart now and check for problems'. This checks for RAM issues that might be misattributed to ACPI.