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WinPE is essentially the Wizard that installs Windows but it is classified as an Operating System. This is a good description.

My question is why is it called an operating system?

I can see that it sets up the PC before Windows can be installed but couldn't WinPE be simply considered a part of Windows? How is it a separate OS?

Is there a comparable thing in Linux world, how does Linux get installed on brand new PC? Does it also require a thin OS?

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    It a "live distro" with the purpose of installing windows. Its like installing Ubuntu after trying it but without the try part.
    – dmb
    Aug 27, 2021 at 3:53
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    WinPE can be configured to run all sorts of things, can even have a desktop, and have applications that exist part of the image. For instance you can run regedit when booting to a Windows installation environment to configure Windows. WinPE can also run virtually any Windows desktop application but there are a few exceptions.
    – Ramhound
    Aug 27, 2021 at 5:18
  • It's comparable to the Linux world where there are various different Operating Systems that are all "Linux" - eg: Android, Ubuntu, Arch Linux, Red Hat Enterprise Linux, SteamOS etc.
    – slebetman
    Aug 27, 2021 at 15:46

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It's not a separate OS, however, it is still an OS. WinPE is just a trimmed down version of Windows – it doesn't show a login screen, doesn't have a taskbar, just directly runs Setup.exe instead, but it nevertheless boots a full OS (the regular Windows kernel, drivers, etc).

So the point of calling it "an OS" isn't to brand it as something completely separate, but rather to indicate that it is not "just the setup wizard". WinPE is Windows, so it is not fundamentally limited to running just Setup – it is only configured to do so.

For example, there's the standard Cmd.exe hidden behind Shift+F10, it comes with many standard tools like Diskpart or Regedit, you can use it as a mostly functional OS. (In the days of Windows XP, you could even run Solitaire or Minesweeper to play while installing.) In fact Microsoft even publish tools for creating your own custom WinPE builds, with your favourite recovery tools included.

In the Linux world, things work exactly the same way. When you boot a Linux CD or USB stick, it just boots a specially prepared Linux distro from a read-only image, but it's still just a Linux distro – the same kernel runs the same init system and starts mostly the same services.

(In particular, if it's branded as a Live CD, it's usually nearly indistinguishable from a full installation, while Install variants tend to be more specialized and trimmed down.)

It is also the same with BSDs, Solaris, and even OpenVMS – when you boot the installer, everything happens in a minified version of the actual OS that you're installing. Nobody writes the whole installer from scratch on bare metal if they can use pre-existing tools (especially pre-existing drivers, as the installer needs to access your disks, your filesystems, etc).

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  • Oh nice I never noticed that minesweeper was runnable from the CD. I wonder of some dev at MS snuck that in.
    – Joshua
    Aug 27, 2021 at 17:31
  • No, I think I used to run it from C:\Windows as it was already copied to the disk at the point the GUI showed up. Aug 27, 2021 at 17:45
  • Ah; that's not PE anymore then. At that stage the setup is running inside actual OS being installed.
    – Joshua
    Aug 27, 2021 at 18:37
  • You say "it ... doesn't have a taskbar", but WinPE certainly supported a taskbar in the Windows XP era, which was the last time I used it. Was support for that removed in modern versions? Aug 27, 2021 at 19:04
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    @Herohtar - The current WinPE most certainly does have a taskbar. The installation environment is separate from WinPE. It most also certainly most definitely has File Explorer.
    – Ramhound
    Aug 28, 2021 at 2:30
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WinPE is Windows. It’s analogous to how Debian is a specific distribution of Linux. WinPE is one of a handful of ‘distributions’ of Windows, alongside the Xbox One system software (Windows 10 with a custom 10-foot UI, with the games actually running in Hyper-V VMs with a minimalist OS kernel), Windows IoT (a specialized variant designed for embedded systems), and a handful of others.

WinPE itself provides a (near) full Windows environment, it just boots to something other than the usual login screen and graphical shell. You can even configure it to do any number of other things. The company I used to work at had a customized WinPE CD for system recovery purposes that booted to a PowerShell session with all the tools we normally used to repair a system.

Linux, BSD, and most other modern operating systems handle things similarly for their installation processes, the installation environment is a largely complete system by itself. Depending on the exact OS and distribution, it may default to a ‘live’ environment where you have to run the installer manually (Alpine Linux, Arch Linux, and most source-based distributions do this), or it may just boot directly to the installer (Debian, OpenSUSE and NetBSD do this).

Obviously, since these are using the standard OS kernel of the system they’re installing, there is an operating system involved, you just don’t usually see it directly (of course, it could be argued that you don’t see the Linux kernel or NT kernel directly either in most cases during normal usage of a Linux or Windows system).

This approach is taken largely because writing the installer like a regular application has a number of benefits:

  • Because it uses the same drivers that the installed system will, you significantly reduce the risk of problems with storage devices or filesystems. This, by itself, eliminates a whole class of potential problems without requiring almost any engineering work.
  • It completely avoids the need to write custom graphics routines if you want a graphical installer (if you’ve never done any embedded or systems-level software development this probably does not sound like a significant benefit, but trust me, it’s huge).
  • Regular applications are exponentially easier to debug than bare-metal stuff. It is possible with good VM tooling to debug a bare-metal application much more easily than used to be the case, but it’s still exponentially easier to just use your regular debugger.
  • If things are designed correctly, it allows users to bootstrap additional installs from an existing install without needing installation media. You can actually do this on many Linux distributions pretty easily, though it’s rather tricky on Windows (it’s doable, but you can't readily leverage the default setup program, and there are a huge number of limitations involved).
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Why is DOS called an Operating System?

It consists of only 2 or 3 files but it has a kernel and a shell for the user to interact with that kernel. Any DOS applications can run on it

Same to WinPE which is vastly more powerful than DOS because it can do anything a normal Windows can do within the capability of the available libraries. Despite the name, it's not a simple installation environment but a full-fledged OS with a kernel and a shell, a long with many supporting utilities

In fact WinPE was significantly commonly used in non-Linux rescue disks (ever heard of the famous Hiren's BootCD?), with many Windows hacking tools like disk partitioner, registry editor, password resetter... pre-installed. None of those apps know that they're running on WinPE instead of Windows unless they explicitly want to, because both are the same thing running the same kernel

Windows PE (WinPE) is a small operating system used to install, deploy, and repair Windows 10 for desktop editions (Home, Pro, Enterprise, and Education), Windows Server, and other Windows operating systems. From Windows PE, you can:

  • Set up your hard drive before installing Windows.
  • Install Windows by using apps or scripts from a network or a local drive.
  • Capture and apply Windows images.
  • Modify the Windows operating system while it's not running.
  • Set up automatic recovery tools.
  • Recover data from unbootable devices.
  • Add your own custom shell or GUI to automate these kinds of tasks.

Windows PE (WinPE)

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It's an operating system in the sense that it's software that's bootable by itself, executable without needing to be launched within another operating system.

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In addition to @Boann, everything that can be bootable (that is, launchable by the BIOS/UEFI) is an operating system from the firmware's point of view.

I mean, the BIOS/UEFI doesn't ever distinguish a fully fledged from a live from a preinstallation OS. It loads the kernel and executes its entry point. The kernel is the only piece of code authorized to interact with hardware and interrupts.

In that sense, since the preinstallation environment must interact with the user with a GUI or a prompt, it must be an OS. An OS that will install another OS on permanent storage? Indeed

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Well, you seem to be coming from this from a perspective of what a webpage tells you about WinPE.

And you perhaps think that WinPE is only the thing that Windows installation uses.

But it's more than that.

You can use WinPE without even knowing that it's part of the Windows installation. I used WinPE before I knew it was somehow part of how windows installs itself.

I remember once somebody's computer went down and I said here use this computer and I let them use a computer that booted off WinPE. They could browse the Internet and run some basic programs.

Infact, if people had issues with, say, deleting a file in windows, and then they could boot off a linux USB/CD and do it from there. Or, sometimes they could alternatively do the Windows equivalent of that and boot off WinPE. Before I knew of WinPE I recall there being a BartPE which was a basic cut down Windows OS which years later I found out was based somehow off WinPE.

Really it's hard to see how somebody can't know that WinPE is an OS. WinPE isn't so well advertised though..

Last time I made a WinPE USB, was I ran a program called Macrium Reflect which makes an image(nowadays one might do that from Windows), and Macrium Reflect has an option to make a bootable rescue WinPE USB.

From there I think you'd manually open macrium reflect.. but could do other things from it too.

It's very obviously a lightweight OS!

Infact, in the uses that i've mentioned, it doesn't pretend to be anything else.

We used to use Boot Disks(Dos boot disks, or Win9X boot disks, which are DOS boot disks), then boot disks converted to USB/CD/DVD.. But then people started using lightweight Linux boots or BartPE or WinPE.. to do fixes without loading windows.. Those are all OSs.

Also you have to look at what is an operating system.. well, it loads pretty early on and stays running, and it's a piece of software that runs other software. That's a far from exhaustive definition but WinPE does fit that. And given the examples i've mentioned it's really impossible to not see it as an OS in those examples. If you only know of it as something that windows installation uses then I can see how you wouldn't know it as an OS.

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