Exploring Windows PE

Windows PE, which is supplied with Windows 7 and in the Windows AIK, is the installation engine for Windows 7. It is directly bootable from CD, DVD, and universal serial bus (USB) flash drives (UFDs). You can also start Windows PE by using Windows Deployment Services and the Pre-Boot Execution Environment (PXE) extensions to Dynamic Host Configuration Protocol (DHCP) (if supported by the network adapters of your computers).

Windows PE is a minimal Windows operating system that provides limited services based on the Windows 7 kernel. It also provides the minimal set of features required to run Windows 7 Setup, install Windows 7 from networks, script basic repetitive tasks, and validate hardware. For example, with Windows PE, you can use powerful batch scripts, Windows Script Host (WSH) scripts, and HTML Applications (HTAs) to fully automate computer preparation and Windows 7 installation, rather than the limited batch commands in MS-DOS. Examples of what you can do with Windows PE include:

• Create and format disk partitions, including NTFS file system (NTFS) partitions, without rebooting the computer before installing Windows 7 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 7. Windows PE provides network access comparable to Windows 7. In fact, Windows PE provides the same network drivers that come with Windows 7, allowing you to access the network quickly and easily. Customizing MS-DOS-bootable disks to access network shares was time consuming and tedious.
• Use all the mass-storage devices that rely on Windows 7 device drivers. Windows PE includes the same mass-storage device drivers that Windows 7 provides, so you no longer have to customize MS-DOS-bootable disks for use with specialized massstorage 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 7, so you are already familiar with the techniques and tools used to customize Windows PE. You can customize it in a variety of scenarios:
  • Addition of hardware-specific device drivers
  • Automation through use of Unattend.xml answer files
  • Execution of scripts (batch, WSH, and HTA) to perform specific actions

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

Windows PE 3.0

Windows PE 3.0, the new version that will be released with Windows 7, is an important part of the deployment process. Even the standard DVD-based installation of Windows 7 uses Windows PE 3.0, and most organizations will be using it (often customized for the organization's specific needs) as part of their deployment processes.

Compared to MS-DOS-based deployment, Windows PE 3.0 brings numerous benefits, including less time spent trying to find 16-bit real-mode drivers. (It's not even possible to find these any more for some newer network cards and mass storage adapters.) Better performance from 32-bit and 64-bit networking stacks and tools, as well as large memory support, are also advantages. And don't forget support for tools such as WSH, VBScript, and hypertext applications.

Windows PE has been available for a few years (the latest version, Windows PE 2.1, was released at the same time as Windows Vista and Windows Server 2008). Previous versions required you to have SA on your Windows desktop operating system licenses. With Windows PE 3.0, that's not the case. All organizations will be able to download Windows PE 3.0 from http://www.microsoft.com and use it freely for the purposes of deploying licensed copies of Windows 7.

Like Windows 7 itself, Windows PE 3.0 is provided as an image that is modular and can be serviced both online and offline. As with Windows PE 2.1, several optional features can be added. New tools like Deployment Image Servicing and Management (DISM) are provided for servicing Windows PE 3.0. You can use DISM to add packages and drivers, including mass storage devices, which no longer require any special handling.