Fix UEFI Boot in Windows 10: Step-by-Step

If Windows 10 won’t boot and you’re stuck in a UEFI/BIOS loop or seeing a “No bootable device” error, the fix usually involves checking your boot order, disabling Secure Boot or CSM, or repairing the EFI boot loader. This guide walks you through the most common causes and step-by-step solutions, from simple BIOS settings to command-line repairs.

What Is UEFI and How Does It Differ from Legacy BIOS?

UEFI (Unified Extensible Firmware Interface) is the modern replacement for the old BIOS (Basic Input/Output System). It’s the firmware that starts your computer, initializes hardware, and hands control to the operating system. Unlike BIOS, UEFI can boot from drives larger than 2 TB, supports faster startup, and uses a special partition called the EFI System Partition (ESP) to store boot loaders.

Windows 10 installs in either UEFI mode (with a GPT partition table) or legacy BIOS mode (with an MBR partition table). The mode is chosen at installation time and is tied to how the drive is formatted. If you try to boot a UEFI-installed Windows from a legacy BIOS setting, or vice versa, you’ll get a boot failure. Most modern PCs default to UEFI, but some older hardware or custom builds still use legacy.

Common Symptoms of a UEFI Boot Problem

Before diving into fixes, recognize the signs:

Computer boots directly into BIOS/UEFI settings instead of Windows.
“No bootable device found” or “Reboot and Select proper Boot device” error.
Black screen with a blinking cursor after the manufacturer logo.
Windows starts but then crashes with a blue screen (BSOD) referencing INACCESSIBLE_BOOT_DEVICE.
Windows shows a recovery screen saying “Your PC/Device needs to be repaired.”

These symptoms usually point to one of three issues: incorrect boot order, a corrupted EFI boot loader, or a mismatch between the firmware mode and the disk partition style.

Step 1: Check Your Boot Order and Firmware Mode

The first thing to try is entering your UEFI/BIOS setup. Restart your PC and press the key shown on screen (often F2, Del, F10, or Esc). Look for a section called Boot or Startup. Ensure your Windows drive (e.g., “Windows Boot Manager” or the drive name) is first in the boot order.

Also check the firmware mode setting, sometimes labeled Boot Mode, UEFI/Legacy, or CSM (Compatibility Support Module). If your Windows was installed in UEFI mode, set it to UEFI (disable CSM or set it to “UEFI only”). If it was installed in legacy mode, set it to Legacy or CSM. If you’re unsure, try both – but note that switching modes may require re-installing Windows if the disk partition style doesn’t match.

Step 2: Disable Secure Boot (Temporarily)

Secure Boot is a UEFI feature that prevents unauthorized operating systems from loading. If it’s enabled but your Windows installation doesn’t have the correct keys (or you’re using a custom bootloader), it can block booting. To disable it, go to the Security or Boot section of your UEFI and set Secure Boot to Disabled. Save changes and restart. If Windows boots, you can leave it disabled or re-enable it later after verifying your system is healthy.

Note: Some PCs require you to set a BIOS password before you can change Secure Boot settings. If you’ve never set one, you may need to create a temporary one.

Step 3: Repair the EFI Boot Loader with Command Prompt

If the boot order and firmware mode are correct, the problem is likely a corrupted EFI boot loader. Windows provides a recovery environment with command-line tools to fix this. Here’s how:

Create a Windows 10 installation USB (using Media Creation Tool) or use a recovery drive.
Boot from the USB. When the setup screen appears, click Repair your computer (bottom-left).
Go to Troubleshoot → Advanced options → Command Prompt.
At the command prompt, type diskpart and press Enter.
Type list disk to see your drives. Identify the system drive (usually Disk 0).
Type select disk 0 (replace 0 with the correct number).
Type list partition to see partitions. Look for the EFI partition (usually 100 MB, FAT32, labeled “System”). Note its partition number.
Type select partition 1 (replace 1 with the EFI partition number).
Type assign letter=S to give it a drive letter.
Type exit to leave diskpart.
Now run these commands to rebuild the boot loader:
- bcdboot C:\Windows /s S: /f UEFI – This copies boot files to the EFI partition. If your Windows is on a different drive letter, adjust C: accordingly.
- bootrec /fixmbr
- bootrec /fixboot
- bootrec /rebuildbcd
Type exit and restart your PC. Remove the USB when prompted.

If you get an error like “The system cannot find the path specified,” make sure the drive letters are correct. You can use dir C:\Windows to verify.

Step 4: Reset UEFI/BIOS to Defaults

Sometimes a misconfigured setting is the culprit. In your UEFI/BIOS, look for an option to Load Optimized Defaults or Reset to Factory Settings. This will restore all firmware settings to their default state, which usually works for most systems. After resetting, re-check the boot order and firmware mode (they may revert to defaults, which is usually UEFI).

Step 5: Use Startup Repair (When Command Prompt Isn’t Enough)

If you’re not comfortable with commands, try the built-in Startup Repair. Boot from the installation USB, choose Repair your computer → Troubleshoot → Advanced options → Startup Repair. This tool automatically scans for boot problems and attempts to fix them. It’s less precise than the command-line method but is often effective for simple boot loader issues.

Frequently Asked Questions

Why does my PC boot straight to BIOS after a Windows update?

Windows updates occasionally change the boot configuration or the EFI boot entry. This can cause the firmware to lose track of the boot manager. Re-running bcdboot as described above usually restores it. Also, check if the update changed your firmware mode (unlikely but possible).

What is the difference between UEFI and Legacy boot mode?

UEFI is the modern firmware interface that supports GPT disks, Secure Boot, and faster startup. Legacy (or CSM) emulates the old BIOS and is used for MBR disks. Windows 10 can run in either, but the mode must match the disk partition style. You can check which mode you’re using by opening msinfo32 in Windows and looking at “BIOS Mode” – it will say UEFI or Legacy.

Can I switch from Legacy to UEFI without reinstalling Windows?

Yes, but it’s not trivial. You need to convert the disk from MBR to GPT using the mbr2gpt tool (available in Windows 10 version 1703 and later). After conversion, you must enable UEFI in the firmware and disable CSM. The process is safe if done correctly, but it’s recommended to back up data first.

What should I do if I see “No bootable device” after changing BIOS settings?

This usually means the boot order is wrong or the firmware mode doesn’t match the disk. Re-enter BIOS and set the correct boot device (e.g., “Windows Boot Manager”). If that fails, check if the disk is detected in the storage settings. If not, the drive may be disconnected or failing.

Is it safe to disable Secure Boot?

Yes, for most users. Secure Boot is primarily a security feature that prevents malware from hijacking the boot process. Disabling it won’t harm your system, but it may make it slightly less secure. You can re-enable it after fixing the boot issue, but if you use Linux or other OSes, you may need to keep it off or enroll custom keys.

Will resetting UEFI/BIOS erase my data?

No. Resetting the firmware settings only changes configuration options, not the data on your drives. Your files, programs, and Windows installation remain untouched. However, it may revert settings like boot order, so you’ll need to re-apply any custom settings.

General steps for current mainstream versions; menus can differ by device and version. See the disclaimer or report an error.

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