While writing my previous post on creating a bootable Windows 10 USB stick on MacOS, I wanted to grab a screenshot of the setup error message that appears when install.wim is not where Windows Setup expects.

Windows could not collect information for OSImage because the specified image file install.wim does not exist

I couldn’t find a way for VirtualBox to boot from a USB storage device, so figured I’d just extract the original ISO, delete the install.wim and build a new ISO image. I’d then be able to boot this in a VirtualBox VM and get myself a screengrab of the error dialog.

Creating a bootable Windows 10 ISO from the contents extracted from the official ISO image took a fair amount of trial-and-error. I finally settled on the following which seemed to work.

  1. Extract the contents of a Windows 10 ISO to a suitable location, let’s call it ~/windows_10_custom

    This can be done by mounting the ISO image and copying the contents using Finder, cp -prv or rsync… whatever your file copying tool of choice happens to be today.

  2. Make whatever custom changes you need to make within ~/windows_10_custom

    In my case I just needed to remove install.wim to reproduce the relevant error message.

    You’ll need to ensure you leave the boot/etfsboot.com file in place if you want the ISO image to be bootable.

  3. Build a new bootable ISO by running the following command

    hdiutil makehybrid -o ~/windows_10_custom.iso -udf -iso -eltorito-boot ~/windows_10_custom/boot/etfsboot.com -no-emul-boot -boot-load-size 8 ~/windows_10_custom

  4. The ISO image will be created at ~/windows_10_custom.iso

Simple as that. Well, it is when you know how.