APC INDEX MISMATCH Error in Windows

The APC INDEX MISMATCH error is a type of Blue Screen of Death (BSOD) that Windows users may encounter. This error indicates a mismatch in the Asynchronous Procedure Call (APC) index, typically caused by software or hardware issues. In this guide, we’ll go over the main reasons behind this error and how to fix it.

What Causes the APC INDEX MISMATCH Error?

Several common causes contribute to this error, including:

  • Driver Issues: Incorrect or outdated drivers are often the primary cause of APC INDEX MISMATCH errors, especially when they conflict with the operating system or other installed drivers.
  • Corrupted System Files: If Windows system files are damaged, it can lead to crashes and errors, including APC INDEX MISMATCH.
  • Hardware Problems: Peripheral devices or components like RAM or graphics cards can occasionally trigger this error due to malfunction or improper operation.
  • Incorrect BIOS Settings: In some cases, unstable BIOS settings can cause this error if they’re incompatible with certain hardware.

How to Fix the APC INDEX MISMATCH Error

1. Update Device Drivers

The first and most straightforward step is to check and update your drivers:

  • Open Device Manager (press Win + X and select the option).
  • Look for any devices with warning icons (a yellow exclamation mark).
  • Right-click the device and choose Update Driver.

If automatic updates don’t resolve the issue, visit the device manufacturer’s website and download the latest driver versions manually.

2. Check Windows System Files

If you suspect corrupted Windows files, you can use the System File Checker tool:

DISM /Online /Cleanup-Image /RestoreHealth
sfc /scannow

Run Command Prompt as an administrator and enter these commands one at a time. This will enable Windows to repair or replace damaged files.

3. Disconnect Peripheral Devices

Certain peripherals, like printers, scanners, or external hard drives, may be causing the APC INDEX MISMATCH error. Try disconnecting unnecessary devices and rebooting your PC to see if the error persists.

4. Check Your RAM

This error can also be related to faulty RAM. Use the built-in memory diagnostic tool:

  • Press Win + R, type mdsched.exe, and hit Enter.
  • Select the option to restart and check for memory problems.

If the test detects any errors, you may need to replace your RAM modules.

5. Update BIOS

In rare cases, updating the BIOS can help resolve the problem. Go to your motherboard manufacturer’s website and follow the instructions for BIOS updates. Be cautious, as improper updates can lead to more serious issues.