When your Windows computer refuses to boot or starts displaying startup errors, it's normal to get nervous thinking you'll have to reinstall everything or that you've lost your documents. Fortunately, there are several tools and commands Advanced solutions that, when properly executed, can resolve the vast majority of boot problems, allowing you to regain control of your system without major complications.
One of the most powerful resources that Windows offers for this type of situations is called bootrec.exeThis built-in utility is specifically designed to repair boot records, damaged sectors, and rebuild startup configurations. In this article, I explain in detail what each of its commands does, how to use them in your specific case, and what to do if you encounter errors during the process.
What is Bootrec.exe and what is it used for?
The tool bootrec.exe is a command that is run from the Windows Recovery Environment (Win). Its main function is to fix boot problems, whether the computer does not turn on or if a message appears such as "Bootmgr is missing", "No required information found in the boot configuration data file" or similar related to the boot sector, MBR, or the BCD store.
Boot problems in Windows can be caused by a variety of reasons: sudden shutdowns, virus attacks, physical or logical hard drive failures, interrupted updates, errors in the boot record, or simple corruption of critical files. That's where bootrec.exe comes in, with a series of commands designed for each type of issue.
First steps before using Bootrec.exe
Before getting into the subject, it is important to highlight that in order to use bootrec.exe You need to access the Windows Recovery Environment. The normal way to do this is by booting the PC from a windows installation disk or a unit Bootable USB with the system. If your computer doesn't start, you'll need to use one of these methods to access the advanced recovery options.
- Boot from DVD or USB Windows installation.
- Press any key when prompted.
- Choose the language and keyboard language, then click Next.
- Instead of "Install Now", select "Repair the computer" in the lower corner.
- Choose Solve problems > Advanced > Symbol of the system.
It is recommended to have a copy of your important files on hand or a backup recent, as in extreme cases you may need to reinstall the system.
Main Bootrec.exe commands and when to use them
bootrec.exe It supports several parameters that solve very specific problems in the boot process. I'll explain the most important ones and when you should use them.
/ FixMbr
This command write a new MBR (Master Boot Record) on the system partition. It doesn't delete the partition table, it just replaces the MBR code, so it's safe if you're worried about losing your data. It's the ideal option if:
- The MBR is damaged by viruses or malware.
- The computer displays errors such as “MBR is missing” or “Operating system not found.”
- You have removed non-standard code at startup (for example, after removing Linux or multiboot software).
/FixBoot
With this command a new boot sector is written on the system partition, using a sector compatible with the version of Windows you have installed. You can use it if:
- You receive error messages such as “Bootmgr is missing” or “The boot sector is corrupted.”
- You have installed an older operating system after Windows and the PC boots with NTLDR instead of Bootmgr.
- The boot sector was overwritten by another program or is corrupted.
/ScanOS
This command scan all disks for Windows installations that are not added to the BCD (Boot Configuration Data) store. This is highly recommended if:
- Your Windows does not appear in the boot menu.
- You have multiple partitions or installations and some are not recognized.
/ RebuildBcd
Perhaps the most powerful: Scans all disks and allows the BCD store to be rebuilt, adding missing Windows installations, and troubleshooting boot configuration file errors. For a deeper dive into how to use these commands, you can check out this advanced guide on boot repair. Here.
If the problem persists after rebuilding the BCD, you can manually export and delete the BCD file and then run /RebuildBcd again to force the creation of a completely new one.
How to run boot repair commands
Once you have opened the command prompt from WinRE, you must enter the commands one by one according to the problem you are experiencing, by pressing Enter after each one:
bootrec /fixmbrbootrec /fixbootbootrec /scanos(Optional)bootrec /rebuildbcd
In many cases, with /fixmbr y /fixboot is usually sufficient, but if the boot menu still doesn't work, also run / rebuildbcdIn more complex situations, it may be necessary to export and delete the BCD file and then rebuild it manually using additional commands such as:
bcdedit /export C:\BCD_Backupattrib c:\boot\bcd -r -s -hren c:\boot\bcd bcd.oldbootrec /rebuildbcd
Common Errors: How to Fix "Access Denied" in bootrec /fixboot
Sometimes the command bootrec / fixboot responds with an annoyed "Access denied"This error is usually related to inconsistencies in the UEFI configuration, the use of incompatible installation media, or permission issues on the EFI partition. To resolve these errors, we recommend checking out our advanced guide for .
Practical solutions:
- Recreate and reconfigure the UEFI partition: Boot into advanced options and launch the command prompt. Use
diskpartto identify and assign a letter to the EFI partition (usually about 100 MB in size) FAT32). Then, use commands likebcdboot C:\Windows /s X: /f UEFIto regenerate the boot files. - Rebuild MBR: If your system uses MBR instead of GPT and the problem is there, run
bootrec /fixmbror use specific third-party tools. - Repair the BCD file: Export, delete, and rebuild the BCD store using the previously mentioned commands; this is useful after partition changes or cloning.
- Run automatic startup repairFrom the advanced options, try the graphical Windows Startup Repair. It can resolve errors in system files or the boot registry.
The most common cause of "Access Denied" is the use of incorrect installation media; in these cases, trying a different USB drive or updating the media creation tool usually resolves the issue.
Windows boot sequence and possible errors
To understand at what point in this sequence the system can fail, it is useful to know its phases:
- BIOS/UEFI Phase: The firmware initializes hardware and searches for a valid disk, running MBR or UEFI code.
- bootloader: Windows Boot Manager Locate the Windows loader (Winload.exe or winload.efi).
- Operating system loader: Windows drivers and kernel are loaded.
- Kernel startup: The kernel and essential drivers are loaded; errors at this stage often cause blue screens.
Depending on the phase at which the interruption occurs, the repair should focus on the hardware, the boot files, or the drivers.
Alternative and complementary methods to repair the boot
In addition to bootrec.exe, Windows offers several tools to troubleshoot boot problems:
Startup Repair
An automatic utility that diagnoses and corrects common errors during the boot process, accessible from the advanced recovery options.
Safe Mode or Last Good Configuration
Boot into safe mode or selecting the last working configuration can help you revert recent changes that cause boot failures.
Disk Check and System File Check
Run chkdsk to detect disk errors, and sfc /scannow to repair damaged files, helping to prevent future problems.
Advanced commands: bcdboot and bcdedit
In cases where the BCD is badly damaged, you can use bcdboot to copy files and rebuild boot data, or bcdedit to manually edit entries, always with caution.
bcdboot C:\Windows /s S: /f ALLbcdedit
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