@Ross, I believe I mentioned the upgrade requirement to v8.1.1 in my Post #3 above, 1st sentence, 2nd paragraph!
I concur, added to the fact that you are attempting to do a non-sanctioned upgrade in VM-mode, who knows if that will work or not.

I haven't done much fooling around with VM and W10 upgrades, since none of my test machines have large enough hard drives to run the VMware software.
I re-read your original post and after looking up your Lenovo machine, it comes with W10 Home or Pro, or can have a downgrade to W7 Pro. Looking on the Lenovo driver support page here:
Link Removed
It appears that Lenovo posts drivers for both W8 and W8.1 both 32bit and 64bit.
However, you didn't precisely answer my question about what your install disc looks like. Did it say Microsoft on it? Or Dell? Or Lenovo? Sorry to be picky here, but since we don't have a photo like the one I provided to you, we are left guessing on exactly what you have. This happens often with upgraders, and they don't understand that there are literally hundreds of flavors of Windows discs in each version such as the W8x version you are talking about. They think that any W8 disc is the same as any other. Not so!!
If it said
Microsoft and you attempt to install your 5 year old Win8 on that computer, it should work, however you'll then have to go the Lenovo driver site I linked to above and download and install all of those drivers onto your new m700 machine. We call this a manual rebuild; but it takes advanced skills to make this work and the install order of the drivers is order-dependent.
If your W8 disc says
"Lenovo" on it, then there is a much better chance it will install most of the drivers, but not all as that machine you have ordered is 5 years newer hardware than any Lenovos that were around back in 2011.

So, you could have driver issues with the W10 upgrade. But, it only might be 1 or 2 drivers such as GPU graphics chip/card or audio drivers; which you could easily fix by downloading the W10 drivers for your m700 from the Lenovo driver support page I gave you above.

The best way to downgrade it really, would be to call Lenovo and order a set of W10 install media (DVD or USB stick) directly from Lenovo and use that W8/8.1 license to install your downgrade. This will of course cost your from
$29-$99 US and obviate the use of your existing W8 media (which really isn't the right media to use for a downgrade!).
If I misunderstood what you are actually trying to do with that old W8 license, I apologize. If
you are looking to downgrade that m700 tiny, the disk you have really isn't the right thing, but a competent computer pro could probably get it to work. Moving that license onto the m700 tiny if you can do it, means that W8 license can never be used again on any other computer you own,

including the existing one you originally bought it for (on the machine that had XP on it).
Hypothetically speaking, if you ordered W7 Pro on the m700 tiny from the factory, and wanted to use the free W10 upgrade to upgrade the m700 to W10, that should work as long as you do it before July 29th as we mentioned in detail in both my post and kemical's post.

That's because that machine comes with a
factory pre-loaded OEM W7 license, which is one of the windows versions included in the W7/8x to W10 free trial offer.
We have another admin who does lots of stuff with VM's and W10 upgrades; so he may respond to this part of your question. (Norway, are you reading this?-Thanks in advance).
Let us know which of these things you are trying to do and we'll advise you further.
BBJ