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Create a Custom ISO for Windows 10 -- Part 6 of 6

By Kari the Finn, guest blogger for Ed Tittel, courtesy of

Note: this blog is Part 6 in a series of 6 parts on the topic of using Sysprep to craft a custom ISO for use in installing Windows 10, aimed at the upcoming Creator’s Update scheduled to become available in mid to late April. Your guest blogger for this series is Kari the Finn, well-known Windows Install expert at He’s the person who put tools together (ESD2ISO and UUP2ISO) that let savvy installers convert Windows OS download files into ISO images that may be used to create bootable installation optical media or USB Flash Drives.

Part 1 covered the intro, and Part 2 started users with installation prep; in Part 3 you learn how to update and customize Windows; Part 4 dug into generalizing a Windows image using the Sysprep utility; Part 5 described how to capture the generalized Windows image and turn it into an installable ISO. Here in Part 6 we conclude by explaining how to update or change that ISO file over time. Don’t let the numbering bother you (Part 1 was an introduction, so step 1 of Kari’s 5-step process appears in Part 2, step 2 in Part 3, and so on…) Here’s Step 5/Part 6:

5. Update / Change ISO

The beauty of using Hyper-V VM as technician machine lies in how easy it makes the job of maintaining and updating a customized install image. I am a Fast Ring Windows Insider. That means I get new pre-release builds frequently and thus, want to upgrade my ISO at the same pace. I’m too lazy to go through this whole process weekly (or more often). The same holds true if I no longer want my custom image to include certain pre-installed software elements, want to update or add new software, or want to change the desktop theme or whatnot.

When I feel like changing the ISO I simply apply the Hyper-V technician virtual machine’s standard checkpoint I created just before sysprepping Windows. I can add and remove software, update software, run Windows updates, apply a new theme, or do whatever else I might want to.

When that’s done, I run Disk Clean-up, create a new checkpoint to be able to restore to this point, and repeat Sysprep, capture a new install.wim and make a new ISO. It’s much faster now. The whole process takes just minutes, because both Windows and basic software are already installed.

Upgrading the Custom ISO

As a Windows Insider I might also be interested in upgrading my ISO. When a new build arrives, I restore the checkpoint I created when the technician machine was fully setup after capturing the install.wim file. I can’t use the checkpoint made in Audit Mode before Sysprep because upgrading Windows in Audit Mode is not possible.

Now, booted to normal mode I can upgrade to the latest Insider Build or the next Feature Update Build using Windows Update or a standard ISO image. When that upgrade completes, I enter the following command in an elevated Command Prompt to restart Windows in Audit Mode:

%windir%\system32\sysprep\sysprep.exe /audit /reboot

Windows restarts, then signs into Audit Mode using the built-in Administrator account. The next thing to do now because my initial user account already exists is to open Settings app > Accounts > Other users and delete all existing user accounts also removing their profile folders. I also delete the custom made install.wim file from last time if it’s still located on the image drive (E: in this example) and check to ensure that the Scratch folder still exists (if not, it must be re-created manually as described in Part 4 of this 6-part opus).

Now a Disk Clean-up, Sysprep, capturing install.wim once again and finally writing a new ISO. That’s it!

For Further Questions or comments…

If you have any questions about this 6-part series, or comments to share, do not hesitate to contact me! Here’s my information:

Kari Finn

Links to All Series Elements

Part 1: Introduction & Overview
Part 2: Install Windows and Prepare Assets
Part 3: Update and Customize Windows, Install Software
Part 4: Generalize Custom Windows Image with Sysprep
Part 5: Capture Custom Windows Image, Create ISO
Part 6: Update/Change Custom Windows ISO