Alternatives ways to create Windows USB?

[sudodus]

Are you sure that you have run VBox in a persistent live host?

An installed system in a fast USB 3 pendrive should do the trick also with 16.04.1 LTS. It should work like my system in an external SSD.

[sudodus]

I was curious and tried to install VirtualBox in a persistent live system of Lubuntu 16.04.1 amd64. It works

But if I remember correctly (from the previous installation), there was one extra thing I had to install: virtualbox-qt, maybe because I installed virtualbox with --no-install-recommends this time (to keep it small).

[C.S.Cameron]

I could not get vbox to install in 16.04 or 16.04.1 flash drive.
VBox 5.1.6.deb from virtualbox.org is working out of the box with 14.04.3 except the hardware lock for several engineering programs does not seem to work.
At least AutoCAD is working acceptably, I always wanted a stand alone ACAD flash drive.
Yeh, I guess the USB3 flash drive is the reason it is faster than the last time I tried.

[C.S.Cameron]

Oops, double post.

[sudodus]

I could not get vbox to install in 16.04 or 16.04.1 flash drive.
VBox 5.1.6.deb from virtualbox.org is working out of the box with 14.04.3 except the hardware lock for several engineering programs does not seem to work.
At least AutoCAD is working acceptably, I always wanted a stand alone ACAD flash drive.
Yeh, I guess the USB3 flash drive is the reason it is faster than the last time I tried.

I made it simple and installed VirtualBox from the Ubuntu repositories (into 16.04.1). I think it will work for you too. (VirtualBox version 5.0.24_Ubuntu r108355 is in the repositories of 16.04).

[C.S.Cameron]

Have they ever got the version of VBox in the repositories able to access pen drives?
When booting from a mkusb 16.04 drive I am not able to install VBox from the Software Centre.

[sudodus]

Yes, after installing the 'Extension Pack', that you download from the VirtualBox web site.

I think 16.04.1 LTS is better than the original 16.04 LTS.

[C.S.Cameron]

I recall playing with vm's on a pendrive back in 2008.
The smallest O/S I could find that would run VBox was NimbleX, just a few KB.
sundar_ima added NimbleX to MultibootUSB, the menuentry for NimbleX can be found there
It worked on a pendrive but was too slow on USB2, (or was it USB1), to be practical.
USB3 looks like a whole new story.

Edit:
Looks to me like minimum footprint on the flash drive using Ubuntu 16.04.1 + VBox 5.1 is about 2GB,
1.4GB for O/S and 210MB for VB, 128GB-2GB leaves 126GB for another O/S and a moderate software collection.
Lots of RAM and USB3 help.

Sudodus is right, install VBox using Software Center.

[C.S.Cameron]

Procedure:
Obtain 128GB USB3 flash drive.
Use mkusb to create a persistent flash drive with 1% persistence.
Safely remove and replug flash drive.
Copy existing virtual machine image, (.vdi), to the "usbdata" partition on the flash drive.
Reboot into the USB
Connect to internet.
In Software & Updates, check "Software restricted by ..., etc.", then select "Updates" and ensure the machine will not will not automatically download or install updates.
In Software Center install VirtualBox,
From www.virtualbox.org/wiki/downloads download the extension pack.
Install the extension pack using VBox.
Run VBox and select New, when you get to Hard disk, select "Use an existing..." and choose the image in usbdata.
Boot the VM and install Guest Additions.
Join vboxusers group.

Results:
So far the drive is working in every computer I try, but slowly in computers without USB3 and/or less than 4GB RAM.
In a computer with lots of RAM some things almost seem faster, like orbiting complex rendered solids in AutoCAD.
AutoCAD 2013 & 2016, SolidWorks, Cosmos FEA, Staad, Autoplant, Rhino and SketchUp all work
Hilti Profis required a new serial number, and CAESAR II and CADWorx required re-installation of hardware locks.
Have had no luck connecting to a VPN.

[sudodus]

Thanks for sharing your experience, C.S.Cameron