WinPE, also called the Microsoft Windows Preinstallation Environment, is a simplified operating system based on a version of the Windows kernel.
WinPE is not intended to be a complete operating system (OS) or provide software application programs with a full suite of services. Instead, WinPE serves as an emergency startup platform that can be used to install, troubleshoot or recover a full Windows environment on a computer. Computer OEMs typically use WinPE to pre-install Windows on a system prior to sale.
WinPE is sometimes called a "Windows boot disk" because it renders legacy DOS boot disks obsolete by providing a richer and more versatile operating environment. For example, depending on the version, WinPE can support storage features such as NTFS, networking through TCP/IP, and 32-bit and 64-bit device drivers.
WinPE can also support basic Windows application programming interfaces (APIs), Windows Management Instrumentation, Windows Script Host, Systems Management Server (SMS) and Windows Recovery Environment. WinPE can also be launched from varied sources such as CDs, DVDs, USB flash drives and Windows Deployment Services.
When used for installation, WinPE collects information about the system hardware and executes the full Windows OS installation. OEMs can tailor WinPE to customize and automate aspects of the installation process. WinPE can also help with troubleshooting when the Windows OS fails to start normally. For example, WinPE can launch diagnostic or recovery tools like Windows RE or other third-party tools, or it can simply start a reinstallation of the operating system.
There are numerous versions of WinPE available. Version 1.x of the Windows XP boot disk was based on Windows XP and Windows Server 2003. Version 2.x used Windows Vista and Windows Server 2008. Version 3.x used Windows 7, and Version 4.0 uses Windows 8. Version 5.0 is the latest version based on Windows 8.1.
WinPE should support prior versions of the Windows OS, so it’s better to use newer versions of WinPE (available in the Windows Automated Installation Kit) to install or repair older versions of Windows. It may not be possible to support newer versions of Windows using older versions of WinPE.