Microsoft Windows Registry Guide, Second Edition

Exploring Windows PE

Windows PE is a supercharged replacement for MS-DOS in your deployment processes. Windows PE is a minimal Windows system that provides limited services based on the Windows XP or Windows Server 2003 kernel, depending on which version of Windows you used to build Windows PE. Windows PE also provides the minimal set of features required to run Windows Setup, install Windows from networks, script basic repetitive tasks, and validate hardware. For example, with Windows PE, you can use more powerful batch scripts, Windows Scripting Host (WSH), and HTML Applications (HTA) to fully automate computer preparation and Windows installation, rather than the limited batch commands in MS-DOS. Here are examples of what you can do with Windows PE:

• Create and format disk partitions, including NTFS file-system partitions, without rebooting the computer before installing Windows on them. Formatting disks with NTFS by using an MS-DOS-bootable disk required third-party utilities. Windows PE replaces the MS-DOS-bootable disk in this scenario, allowing you to format disks with NTFS without using third-party utilities. Also, the file-system utilities that Windows PE provides are scriptable, so you can completely automate the setup-preparation process.

• Access network shares to run preparation tools or install Windows. Windows PE provides network access comparable to Windows. In fact, Windows PE provides the same network drivers that come with Windows, allowing you to access the network quickly and easily. Customizing MS-DOS-bootable disks to access network shares was a time-consuming and tedious process'now it isn't.

• Use all the mass-storage devices that rely on Windows device drivers. Windows PE includes the same mass-storage device drivers that Windows provides, which means that you no longer have to customize MS-DOS-bootable disks for use with specialized mass-storage devices. Once again, Windows PE allows you to focus on important jobs rather than on maintaining MS-DOS-bootable disks.

• Customize Windows PE by using techniques and technologies that are already familiar to you. Windows PE is based on Windows, so you are already familiar with the techniques and tools used to customize Windows PE. You can customize Windows PE for a variety of scenarios, which this chapter goes into in greater detail.

The following sections provide more detail about the features and limitations of using Windows PE. They focus specifically on using it in enterprise deployment scenarios, rather than in manufacturing environments.

Capabilities

Windows PE is a bootable CD that replaces the MS-DOS-bootable disk in most deployment scenarios. (You can start it using Remote Installation Services, too.) It's a lightweight, 32-bit environment that supports the same set of networking and mass-storage device drivers that Windows XP or Windows Server 2003 supports, and it provides access to similar features, including NTFS file system (NTFS) and stand-alone Distributed File System (DFS). Windows PE includes the following features:

• Hardware independence.

  Windows PE is a hardware-independent Windows environment for both x86 and Itanium architectures. You can use the same preinstallation environment on all the desktop computers and servers in your company, without creating and maintaining different bootable disks for different hardware configurations. Say goodbye to that collection of MS-DOS disks.

• APIs and scripting capabilities.

  Windows PE contains a subset of the Win32 APIs; a command interpreter capable of running batch scripts; and support for adding WSH, HTML Applications, and Microsoft ActiveX Data Objects (ADO) to create custom tools or scripts. The scripting capabilities in Windows PE far exceed the capabilities of MS-DOS-bootable disks. For example, the command interpreter in Windows PE supports a more robust batch-scripting language than does MS-DOS, allowing you to create more advanced scripts.

• Network access.

  Windows PE uses Transmission Control Protocol/Internet Protocol (TCP/IP) to provide network access and supports standard network drivers for running Windows Setup and copying source files from the network to the computer. You can easily add or remove network drivers from a customized version of Windows PE. In contrast, customizing MS-DOS-bootable disks to access network shares is frustrating, mostly due to the need to build and maintain numerous disks. Windows PE alleviates this frustration by supporting the network drivers that Windows supports, and Windows PE is easier to customize with additional network drivers.

• Mass-storage devices.

  Windows PE includes support for all mass-storage devices that Windows supports. As new devices become available, you can easily add drivers into or remove them from a customized version of Windows PE. Customizing an MS-DOS-bootable disk to access atypical mass-storage devices requires tracking down and installing the 16-bit device drivers. However, Windows PE supports many of these mass-storage devices out of the box. Also, customizing Windows PE to support additional mass-storage devices is easier because it uses standard Windows device drivers that are readily available.

• Disk management.

  Windows PE includes native support for creating, deleting, formatting, and managing NTFS file system partitions. Also, Windows PE provides full, unrestricted access to NTFS file systems. With Windows PE, you don't have to restart the computer after formatting a disk.

• Support for Preboot Execution Environment (PXE) protocol.

  If the computer supports PXE, you can start it automatically from a Windows PE image located on a Remote Installation Services (RIS) server'and RIS doesn't install the Windows PE image on the computer's hard disk. Starting Windows PE from the network makes it a convenient tool to use in deployment scenarios, and you can easily customize Windows PE directly on the RIS server.

NOTE

You must build a custom Windows PE CD from the Windows PE source files as described in “Customizing Windows PE,” later in this chapter.

Limitations

Windows PE has the following limitations:

• Windows PE doesn't fit on floppy disks, although you can write a custom Windows PE image to a bootable CD.

• Windows PE supports TCP/IP and NetBIOS over TCP/IP for network connectivity, but it doesn't support other protocols, such as Internetwork Packet Exchange/Sequenced Packet Exchange (IPX/SPX).

• The Windows on Windows 32 (WOW32) subsystem allows 16-bit applications to run on the 32-bit Windows platform. The WOW32 subsystem isn't available in Windows PE, so 16-bit applications won't run in 32-bit versions of Windows PE. Similarly, in the Itanium version of Windows PE, the WOW64 subsystem is not available, so applications must be fully 64-bit compliant.

• To reduce its size, Windows PE includes only a subset of the available Win32 APIs. Included are I/O (disk and network) and core Win32 APIs. The following categories of Win32 APIs aren't available in Windows PE (applications that require these APIs do not run in Windows PE):

  • Active Directory Services Interfaces (ADSI)

  • DirectX

  • Microsoft .NET Framework

  • OpenGL

  • Power Options

  • Printing and Print Spooler

  • Still Image

  • Tape Backup

  • Terminal Services

  • User Profile

  • Window Station and Desktop

  • Windows Management Instrumentation (WMI)

  • Windows Multimedia

  • Windows Shell

• Drive letter assignments aren't persistent between sessions. After you restart Windows PE, the drive letter assignments will be in the default order.

• Windows PE supports the distributed file system (DFS) name resolution to stand-alone DFS roots only.

• You can't access files or folders on a computer running Windows PE from another computer.

• Windows PE requires a Video Electronics Standards Association (VESA)'compatible display device and will use the highest screen resolution that it can determine is supported. If the operating system can't detect video settings, it uses a resolution of 640 x 480 pixels.

• You can build custom versions of Windows PE from Windows XP Professional and Windows Server 2003 products, but not from Windows XP Home Edition.

• To prevent its use as a pirated operating system, Windows PE automatically reboots after 24 hours.

• Windows PE doesn't support the .NET Framework.