Booting Windows PE

After creating a custom Windows PE image, you must decide how the image will boot up and where it will run from. The first method is booting from a removable media into random access memory (RAM) and then running directly from a RAM disk. The second method is booting and running directly from a CD or the hard disk.

There are five methods of starting Windows PE by using a RAM disk. You can create bootable Windows PE RAM disk images on:

  • CD-ROM.
  • A USB flash drive (UFD).
  • A hard disk.
  • A Windows Deployment Services (Windows DS) server. You can access the image by way of PXE boot.
  • A supported PXE server. You can access the image by way of PXE boot.

Normally, when you start a computer from a hard disk drive, a CD-ROM, or a Windows DS (PXE) server, Windows keeps operating system file handles open and dedicated to that instance of Windows. Therefore, you cannot remove the CD that you used to start the computer and insert another CD. You cannot delete the hard disk partition from which you started the computer. The Windows DS (PXE) server that is used to start the computer must keep those file handles open, and Windows PE client computers cannot be detached from the network without causing Windows PE to become unstable.

The size of Windows PE enables the entire Windows PE operating system image to load into random access memory (RAM) and to start the computer from a RAM disk. The RAM disk boot feature provides a virtual CD file system in memory.

The Windows operating system Setup Loader now supports loading Windows PE from a RAM disk. The RAM disk driver supports loading an ISO-9660 (CD) image as a RAM disk. Booting Windows PE from a RAM disk enables you to:

  • Swap the CD that is used to start the computer and insert another CD to add drivers, utilities, applications, or a Windows operating system image.
  • Start the computer from a Windows DS (PXE) server with the ability to disconnect from the network once Windows PE has loaded. After the initial download of the Windows PE image, there is no longer any dependency on network resources, such as file handles, which normally must remain loaded until the Windows PE client computer restarts.
  • Delete and repartition the hard disk from which Windows PE has just started.
  • Decrease total boot time.


Windows PE assigns X as the drive letter of any media that it boots from, and the assignment cannot be modified.


The following items are required for starting Windows PE by using a RAM disk:

  • An x86, amd64, or IA64-based computer.
  • A bootable Windows PE image created from a Windows PE 2.0 base image.
  • A minimum of 512 megabytes (MB) of RAM when using the default Windows PE disk image
    If you use a customized RAM disk image, the computer's RAM must be at least 100 MB more than the size of the customized RAM disk image. If there is not enough RAM to store the RAM disk image and to start the operating system, Windows PE will fail to boot.

See Also


Walkthrough: Create a Bootable Windows PE RAM Disk on CD-ROM