Configuring Windows PE

Windows PE supports several configuration files that control startup and operation. These files can be configured to start custom shell environments or perform specified tasks. The available configuration files include:

• BCD store The boot configuration data (BCD) store file contains boot settings for Windows PE.
• Startnet.cmd The StartNet script configures network startup. You can add commands to this script to customize startup.
• Unattend.xml The unattended installation file can be used to automate the installation process for Windows PE.
• Winpeshl.ini The Windows PE shell initialization file contains the default interface for Windows PE. By modifying this file you can define a custom shell environment.

At startup, computers running Windows 7 enter the preboot environment prior to the loading of the operating system. The preboot environment uses Windows Boot Manager to control the boot experience and determine which boot applications are run. The standard boot application for Windows 7 is Windows boot loader. Windows boot loader is responsible for accessing entries in the BCD store. Entries in the BCD store contain boot configuration parameters and control how the operating system is started.

The BCD store is used to abstract the underlying firmware, thereby making it easier for Windows 7 to work with new firmware models such as the Extensible Firmware Interface (EFI). The BCD store also provides the foundation for a variety of new features in Windows 7, including the Startup Repair tool and Multi-User Install shortcuts, which can be launched in the preboot environment.

The BCD store is contained in a file called the BCD registry file. The BCD registry file is located in the \Boot\Bcd directory of the active partition on BIOS-based computers and in the EFI system partition on EFI-based computers. The BCD store contains multiple entries on most computers. These entries include:

• One Windows Boot Manager entry. Because there is only one boot manager, there is only one boot manager entry in the BCD store.
• One Windows boot loader application entry for each Windows 7 operating system installed on the computer.
• One legacy operating system entry.

The legacy operating system entry is not for a boot application. Instead, this entry uses Ntldr and Boot.ini to start up a version of the Windows operating system released prior to Windows Vista. You will use the legacy operating system entry to start up Windows Server 2003, Windows XP, and earlier releases if they are installed on a computer.

Windows PE operates in the Windows PE setup configuration pass of the Windows installation process. During this setup pass, Windows PE looks for an Unattend.xml file. If one exists, Windows PE looks for and reads sections of this file that are used to automate Windows PE setup. You can use the Windows System Image Manager utility, included in the Windows AIK, to create and manage Unattend. xml files. You also can create Unattend.xml files yourself using a text editor. Windows PE looks for the Unattend.xml file in the root directory on the boot device. After you create the file, copy the file to the root directory on the Windows PE boot device. You also can specify the location of this file in the StartNet script or by using the Wpeutil command.

You can initialize Windows PE by using the Winpeshl.ini file. This file is located in the %SystemRoot%\System32 folder in the Windows PE image. In this file, you can specify the path and executable name of a custom shell application that you want to run when Windows PE starts. The Windows Recovery Environment included in Windows 7 is simply a custom Windows PE image that runs a custom shell application.