In the past, IT departments often used an MS-DOS-based boot floppy disk to start a computer, and then either connected to a network share on which a Windows installation source or disk image was located, or did some troubleshooting and recovered the copy of Windows that did not start.
 
However, an MS-DOS-based boot floppy disk has a number of limitations that make it difficult to use for pre-installing Windows or recovering existing installations or data:

• No support for the NTFS files system.
• No support for native networking.
• No support for 32-bit (or 64-bit) Windows device drivers, which makes it necessary to locate 16-bit drivers.
• Rudimentary support for custom applications and scripts.
  
  The limitations of MS-DOS-based boot disks led to the development of Windows PE, now Microsoft’s primary tool for booting computers without a functional operating system. Once you boot a computer into Windows PE, you can prepare the computer for Windows installation and then initiate Windows Setup from a network or local source. You can also service an existing copy of Windows or recover data.
   
  Because Windows PE is based on the kernel for Windows Vista, it overcomes the limitations of MS-DOS-based boot disks by providing the following capabilities:
• Native support for NTFS file system, including dynamic volume creation and management.
• Support for TCP/IP networking and client-side file sharing.
• Support for Windows device drivers.
• Native support for a subset of the Win32 API, scripting and WMI.
• Startable from a number of media, including CD, DVD, USB flash drive (UFD) and a PXE server.

Tip!
To learn more about WinPE, please refer to the “Windows Automated Installation Kit User's Guide” available online from Microsoft as part of the Windows AIK.