Exploring the Windows Boot
Unlike earlier releases of Windows, Windows Vista uses a preoperating system boot
environment. At the core of this boot environment is the Boot Configuration Data
(BCD) data store, which contains boot configuration parameters and controls how
the operating system is started. The preboot environment provides a fundamental
change in the way computers running Windows Vista are started. If you understand
how this preboot environment works, you’ll be better prepared to work with and
troubleshoot Windows Vista installations. Be sure to read this chapter before you
install an earlier version of Windows on a computer running Windows Vista.
Introducing the Windows Vista Boot Environment
Windows computers can use several different processor architectures and several dif-
ferent disk partitioning styles. Generally, computers with x86-based processors use
the MBR disk partitioning style and BIOS. Computers with x64-based processors use
the GUID Partition Table (GPT) disk partitioning style and Extensible Firmware
• BIOS-based computers use Ntldr and Boot.ini to boot into the operating system.
Ntldr handles the task of loading the operating system. Boot.ini contains the
parameters that enable startup, including identity of the boot partitions.
Through Boot.ini parameters, you can add options that control the way the oper-
ating system starts, the way computer components are used, and the way operat-
ing system features are used.
• EFI-based computers use Ia64ldr.efi, Diskpart.efi, and Nvrboot.efi to boot into
the operating system. Ia64ldr.efi handles the task of loading the operating sys-
tem. Diskpart.efi identifies the boot partitions. Nvrboot.efi contains the parame-
ters that enable startup.
Through Boot.ini or Nvrboot.efi parameters, you can add options that control the
way the operating system starts, the way computer components are used, and the