I changed something in BIOS or legacy UEFI and now can’t use PC

Troubleshooting BIOS and UEFI Settings Causing Boot Failures: A Step-by-Step Guide

If you’ve recently modified BIOS or UEFI firmware settings and your PC no longer boots properly, you’re not alone. Such issues can occur when changing advanced settings like TPM, CSM support, or Secure Boot, especially if not configured correctly. Below is a comprehensive overview of common causes and recommended troubleshooting steps to resolve boot problems after BIOS adjustments.

Understanding the Context

In some cases, users may enable features such as TPM (Trusted Platform Module) or Secure Boot to meet specific requirements—like installing or upgrading security features or participating in particular beta programs (e.g., Battlefield 6 beta). However, changing these settings without proper configuration can lead to system boot failures, including automatic repair loops or error screens.

Common Scenario Recap

• User attempts to enable TPM to access game beta features.
• Changes UEFI/BIOS settings, such as enabling TPM, adjusting CSM (Compatibility Support Module), and turning Secure Boot on.
• Upon reboot, the system encounters errors, attempting automatic repairs, but ultimately fails to boot Windows.

Root Causes and Considerations

1. Mismatched Secure Boot and TPM Settings: Enabling Secure Boot without proper configuration can prevent Windows from booting if the system is not booted in the correct mode.
2. Incorrect CSM (Compatibility Support Module) Settings: Switching between UEFI and Legacy modes can cause boot conflicts.
3. BIOS Settings Not Properly Saved or Corrupted: Some changes might not persist or may corrupt the boot process.
4. Corrupted Boot Files or System Files: Sometimes, changes trigger or expose underlying system issues.

Recommended Troubleshooting Steps

1. Reset BIOS/UEFI Settings to Defaults

• Power off your PC.
• Enter BIOS/UEFI firmware setup (typically via pressing Del, F2, or Esc at startup).
• Choose the option to load “Optimized Defaults” or “Reset to Default Settings.”
• Save changes and restart.

Note: This restores BIOS settings to a known good configuration and often resolves boot loops caused by incorrect manual changes.

2. Disconnect External Devices

• Remove any peripherals that are unnecessary, such as external drives or USB devices, which might interfere with the boot process.

3. Repair Windows Startup

• Boot your system from a Windows 10 installation media (USB/DVD).
• Select “