Windows Vista Boot Process Overview

The Windows Vista™ bootYou can use Bcdedit.exe to modify the Windows
process differs from WindowsÂ(R) XP in thecode which runs in the pre-operating system
way the operating system is located and initialized.environment by adding, deleting, editing, and
Start-up begins with the BIOS loading the Masterappending entries in the BCD store. Bcdedit.exe is
Boot Record (MBR) on the bootable disk. The MBR inlocated in the WindowsSystem32 directory of the
turn loads the Partition Boot Record (PBR) on theWindows Vista partition.
active partition. So far, Windows Vista remainsBoot.ini Compared to BCD
relatively unchanged.BCD eliminates the need for Boot.ini in Windows
Windows Vista is different from XP starting by theVista, although Boot.ini is still present on dual-boot
fact the PBR code written by Windows Vista nosystems for backwards compatibility. Because the
longer looks for Ntldr. The new boot loader inBCD boots to the boot environment first instead of
Windows Vista is Bootmgr. This component loads theNtldr, the location of Ntldr is not verified unless a
Boot Configuration Database (BCD), which in turnlegacy operating system is chosen.
loads an OS loader boot application (Winload.exe, inConfiguration Tools
the case of Windows Vista). Finally, the OS loaderThe BCD store can be modified or repaired using
application is responsible for initializing the kernel. Thisseveral tools:
process is illustrated below.System Properties in Control Panel
You can think of this change in two elements:SystemPropertiesAdvanced.exe
The two key actions performed by Ntldr in previousMsconfig
Windows versions have been divided between twoWindows Recovery Environment (WinRE) Startup
components:Repair
1. Bootmgr reads the boot configuration, includingBcdedit.exe
device and path locations.Bootrec.exe
2. WindowsSystem32Winload.exe initializes the kernel.Most of these tools enable you to perform simple
The boot configuration stored by Boot.ini in previoustasks, such as setting a boot menu timeout, setting a
Windows versions is now stored in an extensibledefault operating system, or configuring boot options
database, BootBCD, the Boot Configuration Databasesuch as /SOS and /SAFEBOOT. Others are
(BCD).repair-oriented tools; Startup Repair and Bootrec.exe,
These changes are significant because of the impactin particular, provide automated mechanisms for fixing
they have:problems in the BCD.
1. The boot process can be extended to supportBcdedit.exe is the main tool for detailed BCD store
other applications, such as other operating systemsmodifications. You can use Bcdedit to change
or other versions of the OS.Bootmgr options; add boot, delete, and edit boot
2. Only nonversion-specific components are stored inentries; import and export the BCD store; and create
the root of the active partition. This means thata new store if it becomes significantly damaged.
theoretically Windows Vista could be installed on aBcdedit.exe is located in the WindowsSystem32
machine running some future Windows version withdirectory of the Windows Vista partition and is also
the same boot structure, and it would not break theavailable in WinRE.
boot process for that future version. With legacyBCD Store Location
Windows, installing an older Windows version lastThe BCD store is a registry hive, stored as BootBCD
causes the newer version to fail on start-up. This ison the active partition. This hive is loaded but hidden
due to version-specific code improvements in Ntldr.from view in Regedit.exe within Windows Vista. The
3. Tool-oriented boot entries can be supported tostore is loaded to the following registry location:
offer maintenance options on boot when a previousHKLMBCD00000000.
start-up failed. In the past, Windows supported anYou can also view the store manually in WinRE by
menu provided by a target operating system. Thisloading the hive from the Boot folder. To obtain a
new structure can make tools available earlier duringcopy of the hive on a running system, use the
the boot process, meaning that they are availableBcdedit /export filename command to export a hive
even if all OS-specific boot entries are damaged. Thefile for offline examination. This command exports
Windows Memory Diagnostic tool is provided in thethe BCD store to a file called filename in the current
boot menu in this way.directory.
BCD StoreRelated Components
The Boot Configuration Data (BCD) store containsMsconfig
boot configuration parameters and controls how theMsconfig is the preferred PSS UI tool for managing
operating system is started in Microsoft Windowsboot settings. The tool supports BCD and allows the
Vista operating system. These parameters wereuser to enumerate all BCD objects in the system
previously in the Boot.ini file in BIOS-based operatingstore. It allows certain elements to be altered for
systems or in the nonvolatile RAM (NVRAM) entrieseach OS object, including debug settings, safe mode
in Extensible Firmware Interface-based operatingsettings, and other popular PSS options. It cannot be
systems. You can use the Bcdedit.exe command lineused with the WinRE console; Bcdedit needs to be
tool to affect the Windows code which runs in theused in these cases.
pre-operating system environment by adding,Bcdedit.exe
deleting, editing, and appending entries in the BCDBcdedit.exe is a command line tool that can be used
store. Bcdedit.exe is located in theto manage BCD settings. In summary, Bcdedit.exe is
WindowsSystem32 directory of the Windows Vistaa replacement for Bootcfg.exe. However, it is
partition.enhanced for better scripting and to expose some of
The BCD is a database used by Bootmgr. It containsthe more powerful features of BCD that bootcfg.exe
the functions of Boot.ini and is located in thedid not expose for manipulating Boot.ini. Bcdedit.exe is
{ActivePartition}boot folderdesigned to work on previous operating systems and
Bcdedit.exein recovery environments.