WINLOAD.EXE

The startup process of Windows Vista, Windows Server 2008 and their successors differs from the startup process part of previous versions of Windows.

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 (BCD) is a firmware-independent database for boot-time configuration data. It is used by Microsoft's new Windows Boot Manager and replaces the boot.ini that was used by NTLDR.

Boot Configuration Data are stored in a data file that has the same format as the 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.

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Wikipedia