In this article, unless otherwise specified, what is said about "Windows Vista" also applies to all later NT operating systems. For Windows Vista, the boot sector loads the Windows Boot Manager (a file named BOOTMGR on either the system or the boot partition), accesses the Boot Configuration Data store and uses the information to load the operating system. Then, the BCD invokes the boot loader and in turn proceeds to initiate the Windows kernel.
Windows Vista introduces a complete overhaul of the Windows operating system loader architecture. The earliest known reference to this revised architecture is included within PowerPoint slides distributed by Microsoft during the Windows Hardware Engineering Conference of 2004 when the operating system was codenamed "Longhorn." This documentation mentions that the Windows operating system loader would be undergoing a significant restructuring in order to support EFI and to "do some major overhaul of legacy code." The new boot architecture completely replaces the NTLDR architecture used in previous versions of Windows NT.
Boot Configuration Data is stored in a data file that has the same format as Windows Registry hives and is eventually mounted at registry key [HKEY_LOCAL_MACHINE\BCD00000] (with restricted permissions). For UEFI boot, the file is located at
/EFI/Microsoft/Boot/BCD on the EFI System Partition. For traditional BIOS boot, the file is at
/boot/BCD on the active partition.
Boot Configuration Data may be altered using a command-line tool (bcdedit.exe), using Registry Editor (regedit.exe), using Windows Management Instrumentation, or with third-party tools such as EasyBCD, BOOTICE, or Visual BCD Editor.
Boot Configuration Data contain the menu entries that are presented by the Windows Boot Manager, just as boot.ini contained the menu entries that were presented by NTLDR. These menu entries can include:
Boot Configuration Data allows for third-party integration, so anyone can implement tools like diagnostics or recovery options.
The Windows Boot Manager invokes winload.exe—the operating system boot loader—to load the operating system kernel executive (ntoskrnl.exe) and core device drivers. In that respect, winload.exe is functionally equivalent to the operating system loader function of NTLDR in prior versions of Windows NT. In UEFI systems, the file is called
winload.efi and the file is always located at
If the computer has recently hibernated, then
bootmgr will instead invoke
winresume.exe. The only difference is the alternate boot mode and the splash screen displaying "Resuming Windows". In UEFI systems, the file is called
winresume.efi and is always located at
With the advent of the new boot manager in Windows Vista, many components have been changed; one is the Advanced Boot Options menu that provides options for advanced boot modes (i.e. Safe Mode). Due to the implementation of Hybrid Boot in Windows 8 and up, access to the Advanced Boot Options menu has been disabled by default. However, access is still possible with a BCD modification. These are the possible boot modes:
explorerat the command prompt.
ntbtlog.txt, a file that will log the boot process; listing drivers that loaded and drivers that did not.
The ABO menu is accessible by rapidly pressing or holding the
F8 key before Windows boots.