It is the first program launched by the BIOS or UEFI of the computer and is responsible for loading the rest of Windows.

In Microsoft Windows, the MBR boot code tries to find an active partition (the MBR is only 512 bytes), then executes the VBR boot code of an active partition.

The VBR boot code tries to find and execute the bootmgr file from an active partition.

[8] Boot Configuration Data may be altered using a command-line tool (bcdedit.exe), using the Registry Editor[6] (regedit.exe), using Windows Management Instrumentation, or with third-party tools such as EasyBCD, BOOTICE,[9] or Visual BCD Editor.

[10] Boot Configuration Data allows for third-party integration, so anyone can implement tools like diagnostics or recovery options