What Is Windows Boot Manager in BIOS?

Windows Boot Manager is an application provided by Microsoft for boot environment setup. Individual boot programs launched by the Boot Manager inside the boot environment offer functionality for all customer-facing scenarios before the device starts. But what does Windows Boot Manager do to make a device boot smoothly? In this post, we’ll show you more about Window Boot Manager and how to manage boot device on your PC easily.

What is Windows Boot Manager in BIOS and UEFI?

The Windows Boot Manager, or BOOTMGR, is a bootloader developed by Microsoft for Windows NT versions beginning with Windows Vista. It serves as the initial program initiated by the computer's BIOS or UEFI, with the primary function of loading the remaining components of Windows.

During the boot process, the boot sector, or UEFI loads the Windows Boot Manager from a file named BOOTMGR, located either on the system partition or the boot partition. The Boot Configuration Data store is then accessed to gather relevant information, which is utilized to load the operating system via winload.exe or winresume.exe.

Since BIOS and UEFI both need the bootloader to launch the device, what’s the difference between them?

♦ Windows Boot Manager in BIOS

BIOS is a firmware interface that initializes hardware components and gives the instructions needed to boot the computer. For numerous decades, it has been the typical firmware used in computers.

The boot process in BIOS-based systems begins with the power-on self-test, which checks the system hardware for any problems. When the test is over, the BIOS looks for a bootable device, which is usually a hard drive or an external storage device.

In BIOS, the Windows Boot Manager is in charge of identifying the bootable device and loading the operating system into memory. It reads the master boot record, also called MBR, or boot sector of the active partition, which includes the instructions needed to start the Windows operating system.

♦ Windows Boot Manager in UEFI

UEFI is the successor to BIOS and provides enhanced capabilities and flexibility during the boot process. UEFI has become the standard firmware for modern computers. The boot process in UEFI systems differs from BIOS. It begins with the firmware initializing the hardware components and then executing the UEFI firmware itself. The UEFI firmware contains boot-related data stored in the EFI System Partition (ESP).

The Windows Boot Manager in UEFI is located within the EFI System Partition and is responsible for identifying and launching the Windows operating system. On systems with UEFI firmware, UEFI invokes bootmgfw.efi from an EFI system partition at startup, starting the Windows Boot Manager that utilizes boot entries and boot options stored in the UEFI firmware to determine the appropriate operating system to load.

How do I use Windows Boot Manage?

The Windows Boot Manager may be accessed by hitting the 'F8' key as soon as your machine boots up. If you wish to access Windows Boot Manager while your computer is operating, go to Settings.

Step 1. Open the Settings app from the Start menu.

Step 2. Click Update & Security.

Step 3. Click Recovery from the menu on the left side of the window.

Step 4. Click Restart Now under the Advanced Startup options.

After you enter Windows Boot Manager, you can start to change settings or switch boot device on your computer. Normally, users can use Windows Boot Manager to do the following tasks:

• Operating system selection: If multiple operating systems are installed on the computer, BOOTMGR provides a menu for users to choose which OS to load.
• Hardware initialization: BOOTMGR initializes and configures essential hardware components, such as the processor, memory, and peripherals, to ensure the proper functioning of the operating system.
• Boot configuration data (BCD): BOOTMGR accesses and interprets the BCD store, a database that contains boot configuration parameters, such as boot options, device paths, and startup settings.
• Error handling: If any issues occur during the boot process, BOOTMGR displays error messages and provides troubleshooting options, allowing users to diagnose and resolve boot-related problems.

Further reading: How to easily and quickly manage boot device without entering BIOS?

Windows Boot Manager offers many practical features for users to change device settings. But, different computers from different brands have specific ways to enter BIOS. You need to search how your computer can enter BIOS previously. If you just want to change the boot order and manage boot devices, this process is a little cumbersome.

So, here we recommend you AOMEI Partition Assistant Professional to employ “UEFI BIOS Boot Options Manager” function. This feature allows users to switch boot order while PC is running normally, and also back up current boot settings. What’s more, the program will list all boot settings and information of your devices, so you can see all boot devices, even anomalous boot order can be detected, users can also delete unnecessary boot options via this feature.

Step 1. Install AOMEI Partition Assistant, click “Tools” in the top menu, and choose “UEFI BIOS Boot Options Manager” function.

If your system drive is an MBR one, after you click the tool you will get a message that the feature is available only if the current system disk is GPT partition type.

On a GPT drive, the UEFI Boot Options Manager will pop up. In this interface, all UEFI boot orders on your computer will be displayed and you can manage them.

1. How to change boot options

Click a boot option and click the button up and down to change the boot sequence of your computers.

2. How to delete boot options

Click a boot option that is not available or unnecessary to delete the boot option. Please be cautious before you delete a boot option. For system boot and security, it will be unable to delete the current boot option.

3. How to enable one-time boot entry

Click a boot option and click the button to enable a one-time boot entery. Once you click the option, the computer will boot from this entry only the next time system startup. After the PC boots from the entry once, the PC will boot from the defaulted first entry.

4. How to backup boot options

Click the boot option you want to backup to make a backup so that you can recover if necessary.

Select a location on your PC and click "Save" to save the backup.

Then the backup will create a .PAUB file.

5. How to Restore Boot Options

Click to restore the boot option you just backed up if the partition or boot files get lost or corrupted.

Locate the .PAUB FILE you backed up and select it to restore.

If you have a backup of your boot entries with Partition Assistant and your system cannot boot, you can also create a bootable media with Partition Assistant and restore the boot entries under WinPE.

6. How to refresh boot options

Click the button to refresh the boot options. The "Refresh" button does not mean reset. If you have modified the boot options, the button does not help to reset the boot options.

7. How to boot into UEFI BIOS Boot Options one-time

Please just click the option "Enter UEFI BIOS configuration interface directly only at next boot time".

If you tick this option, the computer will directly boot into the UEFI BIOS configuration interface at the next boot time. After the option is executed once,  your computer will still boot from the defaulted first entry.

There is no need to press any hotkey during the next system boot, for example, DEL or F12. In this way, the UEFI BIOS Boot Manager will be launched so that you can easily change boot sequence or configure other BIOS settings.

After you manage the boot options, you can click the "Restart Now" button to restart your computer immediately if needed.

To sum up

Windows Boot Manager is a vital component in both BIOS and UEFI systems. Whether you're using the traditional BIOS or the modern UEFI, the boot manager is responsible for loading the operating system into memory. AOMEI Partition Assistant can help you manage boot devices much easier when you need them.

Besides boot manager, this tool can also clone disk, migrate OS, convert a disk to MBR/GPT without data loss, move installed apps, allocate free space… And it has the Server Edition for Windows Server users and other advanced editions for your higher requirements.