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If Windows files are still readable but the PC will not start Windows, the EFI System Partition, its Boot Configuration Data (BCD), or the firmware boot entry may still be missing or damaged. Rebuilding the boot files can help, but first verify the Windows volume and EFI partition from the recovery environment: their drive letters may differ from the ones you see during normal Windows use.
This guide covers a Windows UEFI/GPT installation. Readable Windows files alone do not prove the disk, EFI partition, BCD store, or firmware entry is healthy. If the Windows volume is unreadable, the PC uses legacy BIOS/MBR, or Windows is installed across multiple disks, stop and adapt the repair rather than applying the example commands blindly.
What this repair does—and what it does not
On a UEFI system, the EFI System Partition and the Windows OS partition have separate jobs. The EFI partition holds boot files, including Windows Boot Manager at EFIMicrosoftBootBootmgfw.efi; the Windows installation contains the OS loader at WindowsSystem32Winload.efi. A readable Windows directory does not establish that either boot file, the BCD store, or the firmware’s boot entry is in working order. Microsoft’s UEFI BCD documentation describes these paths.
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BCDBoot copies boot-environment files from the Windows directory you specify to a system partition and creates or initializes BCD data there. Microsoft documents it as a way to recreate system-partition files using copies from the Windows partition. Read the BCDBoot command reference before changing options or partition contents.
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Open a recovery command prompt
Use Windows Recovery Environment, Windows installation media, or Windows PE. To use installation media, boot from it and press Shift+F10 to open a command prompt; Microsoft’s BCDBoot repair guidance also describes using WinPE. Microsoft BCDBoot instructions
If you do not already have recovery media, a USB flash drive can be used to create or boot Windows installation media. Follow Microsoft’s media-creation guidance for your Windows edition; this repair does not require a particular drive capacity as a universal rule.
Identify the Windows and EFI volumes in recovery
Do not assume Windows is on C:. WinPE can assign letters differently, and attached USB drives can affect the assignment. Microsoft explains drive-letter assignment in WinPE. First list the volumes:
diskpart
list volume
exitLook for the Windows NTFS volume and the EFI System Partition. The EFI partition is normally FAT32; Microsoft’s UEFI example uses a 200 MB system partition, but that is an example—not a universal size requirement. Microsoft UEFI BCD example
If the verified EFI partition has no drive letter, assign a temporary one in DiskPart only after you have positively identified the partition. Microsoft’s example assigns S: to the system partition. Then leave DiskPart and verify both letters yourself: check that the candidate Windows volume contains a Windows directory and that the temporary letter belongs to the EFI partition. The letters D: and S: below are examples only.
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For a confirmed UEFI/GPT installation, with D:Windows verified as the intended Windows directory and S: verified as the EFI System Partition, the explicit-target pattern is:
bcdboot D:Windows /s S: /f UEFIReplace both example letters with the ones you confirmed in recovery. With /f UEFI, Microsoft requires /s to identify the system partition. On UEFI/GPT, UEFI is the default firmware type; /f ALL writes both BIOS and UEFI boot-file directories and is not needed just because a disk is readable. BCDBoot option reference
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Understand the firmware-entry effect of /s
The /s option selects the destination system partition, but it has an important side effect: when used, BCDBoot does not create a Windows Boot Manager NVRAM entry in that invocation. It relies on the firmware’s default settings to locate the system partition. Without /s, BCDBoot selects a system partition itself and, by default, creates or updates a firmware entry. That default selection may be ambiguous on a computer with multiple disks or system partitions, so do not omit /s without considering which partition the command will choose.
If you need to control UEFI boot order, /p preserves the existing order and /addlast appends the Windows Boot Manager entry. These options cannot be combined. They do not remove the need to verify which Windows installation and system partition are involved. BCDBoot command-line options
Why the UEFI command is not a BIOS/MBR repair recipe
This procedure targets UEFI/GPT. A legacy BIOS/MBR installation uses a different boot path and system-partition arrangement; do not run the UEFI command as a generic fix for every PC. BCDBoot’s /f ALL option writes both BIOS and UEFI boot-file directories, but that does not by itself determine the correct partition layout or firmware configuration for a particular machine.
Do not format or repartition as a first step
Formatting the system partition is listed as an optional operation in Microsoft’s repair reference, not a required opening step. Formatting can destroy files on the target partition. Do not format, delete, create, or change a partition type unless you have confirmed the target, understood the layout, and protected any contents you need. This standard recovery flow does not require those operations. Microsoft BCDBoot reference
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Restart and select Windows Boot Manager if the firmware presents a boot menu. Confirm that it starts the intended Windows installation. If the PC still fails, return to recovery and recheck the volume mapping rather than repeatedly running BCDBoot against unverified targets.
For further diagnosis, Microsoft’s boot troubleshooting guidance recommends checking the BCD entries: for {bootmgr}, inspect the device and path; for {default}, inspect device, path, osdevice, and systemroot. The expected UEFI paths are EFIMicrosoftBootBootmgfw.efi for Windows Boot Manager and WindowsSystem32Winload.efi for the Windows loader. Microsoft boot troubleshooting guidance and UEFI BCD path documentation.
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