You're going about this the wrong way. Don't think in terms of "usb HDD booting windows" and "offloading a cloned image" but rather in terms of creating an intermediary file and copying the contents of that "hd image" to other computers. Doing that can be done while booting temporary operating systems to create the image and to copy it to the target systems (a.k.a. to "deploy" it). Here is the workflow:
- Boot a temporary operating system on the source computer
- Image the system to a single compressed file
- Place that file on a usb thumb drive
- Boot a temporary operating system on the target computer, optionally using said USB
- copy the image to the target internal HDD (a.k.a. "image the target system")
- reboot target system
I created some scripts that automate most of this process and created a thread for it:
ADK Tools Thread
The idea for the project is to automate creating the USB drive that you can use to capture and deploy the image including the installation of the ADKs and the files to copy to the USB thumb drive.
There is also an automation script built in to deploy any number of custom and/or rtm images provided the target system does not require data retention.
Creating the image is the "hard" part.
If you are not comfortable with a command prompt, then my recommendation is to combine the USB thumb drive scripts with this tool: GImagex.
Copy it to the root of the flash drive, copy the following files into the gimagex folder (either x86 or x64 or both) obtained from either version of the ADK (8.1 or 10)
[...]browse to the amd64\DISM folder.
4. Copy the following files into the same folder as gimagex.exe:
imagex.exe (optional, but handy if you also want to use the orginal command-line version of imagex)
And then when you boot, launch it by doing E:\gimagex\x64\gimagex.exe and that should launch the graphical interface by which you can use to create a .wim file. Be sure to save it onto the flash drive.
Then just transfer the flash drive to the target system and install the image using the built-in automated installer.
If you are comfortable with a command prompt then you can skip the gximage thing and use the "image.bat" or "dism.exe" tools to create the image directly. The syntax is something like
image /capture C: E:\Windows81Enterprise_x64.wim
to get the exact syntax. Same thing with the dism tool,
dism /capture-image D: /wim-file:d:\captured.wim [...]
Try to use "fast" compression for the image instead of max. "Fast" is more reliable.