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

Troubleshooting BIOS and UEFI Settings: Resolving Boot Issues After Configuration Changes

Introduction

Adjusting BIOS or UEFI settings can be necessary for enabling particular features or optimizing system performance. However, improper changes may lead to boot failures or system errors. This article discusses common issues encountered after modifying BIOS/UEFI configurations and provides a step-by-step guide to resolve them.

Scenario Overview

Consider a user attempting to enable Trusted Platform Module (TPM) support in order to participate in the Battlefield 6 beta. The user located the TPM option within BIOS/UEFI, enabled it, and also modified related settings such as Compatibility Support Module (CSM) and Secure Boot. Upon saving and rebooting, the system encountered startup issues, including:

A “Repairing your device” screen that fails to resolve itself
A blue screen with options for advanced troubleshooting
Boot loops when attempting to start Windows
Failure of system reset or restoration options
Persistence of boot failure despite resetting BIOS to default settings

Understanding the Causes

Alterations to BIOS/UEFI settings—particularly those related to secure boot, CSM, and TPM—can impact system startup stability. These changes may:

Inadvertently disable essential boot components
Conflict with existing Windows installation
Affect the boot mode (UEFI vs. Legacy BIOS)
Introduce incompatible firmware settings

Step-by-Step Troubleshooting Guide

Reset BIOS/UEFI to Default Settings
Enter the BIOS/UEFI firmware during startup (commonly by pressing F2, DEL, or ESC).
Locate and select “Reset to Defaults” or “Load Optimized Defaults.”
Save changes and exit.
This action reverts all manual modifications and can resolve configuration conflicts.
Verify Boot Mode (UEFI vs. Legacy)
After resetting, confirm that the boot mode matches your Windows installation.
For most modern systems, UEFI mode is recommended.
If Windows was installed in UEFI mode, ensure that Secure Boot is enabled and CSM is disabled.
If Windows was installed under Legacy BIOS, adjust accordingly.
Disable or Reconfigure TPM and Secure Boot
Revisit the BIOS settings:
- Disable TPM temporarily to test if it causes the boot issue.
- Set Secure Boot to Disabled if modifications caused instability.
After testing, re-enable TPM and Secure Boot if