Let’s say you’ve been meaning to install Windows 10 on a test machine, but you haven’t gotten around to that just yet. Because MS has already released another version of the Windows 10 Preview, this might mean you’d have to download and install the original build (9841), then do likewise for the latest version (Build 9860) to play catch-up. “Wouldn’t it be easier,” I can hear many readers grumble, “if MS just provided a new ISO file so that those just getting started with Windows 10 could just install 9860 in one fell swoop?” Alas, that’s not what MS provides, but there is a way to get there from what is available, thanks to Chris Holmes, an automotive electrician from NYC who dabbles pretty seriously with Windows stuff as an avocation (and thanks also to Sergey Tkachenko of WinAero.com for alerting me to this possibility by posting a nicely illustrated blog about an ESD Decrypter tool and how to put it to work).
Holmes has actually blogged on this topic himself in a post called “Make an ISO for Windows 10 9860,” wherein he describes how to take the ESD file from the 9860 Win10 update and convert it into an ISO for direct installation. ESD stands for electronic software download, and for Windows updates, it refers to an encrypted and heavily compressed Windows Imaging Format, or .wim, file. This file is part of the download for the 9860 update: it’s named install.esd and it resides in C:\$Windows.~BT\Sources while the download and install process is underway.
Once you’ve downloaded and installed the ESD Decrypter tool, you can use it to create what the program calls a “traditional Windows ISO” from the install.esd file you’ve obtained and stashed in a directory of your choosing. You can either shell out of the download and install runtime environment on a Windows PC while the install gets underway and save a copy of install.esd, or you can grab the x64 or x86 versions of that file directly online (thanks to links from Tkachenko’s blog post on the subject). Either way, you’ll run the decrypt.cmd file from an administrative command prompt windows, and type the number 4 at the command prompt input line to build a traditional ISO image. From there, you can use Rufus to construct a bootable UFD installer for the latest Windows 10 build, and be off and running with the latest version without first having to install Build 9841 and immediately upgrade it to Build 9860. I like it, and you probably will, too! In fact, this is a nice addition to my overall Windows image management toolkit.