Keith Nuttle wrote:
I bought a HP Stream 7 tablet with 32GB of storage. It came with Window
8. I installed Windows 10 but in the several revision have lost the
Recovery partition to increase free space, so don't have access to the
OEM installation.

Over the period I am having increasing problems installing the Windows
10 updates, because of the small size of the CPU and the limited storage.

I have two questions.

1. If I revert to Windows 8, will I gain enough free space, that it
will continue to update through the period of MS support?

2 If I do revert to Windows 8 will the product Key that I used to
update to Windows 10, allow me to downgrade to Windows 8 using the same
Key? (The computer was purchased about 6 month before Window 10 came
out so the key is on the computer.

If the tablet has a Win8 MSDM key inside the BIOS, then
Windows 8 should automatically activate. That's the whole
purpose of it (no COA sticker).

You can extract the key if you want. Try a search on MSDM
for ideas. For example, I could definitely do it from Linux,
by dumping that particular ACPI table. It should be just as easy
on Windows... as long as someone wrote some code to do it.

The Windows 10 licensing arrangement uses a Digital Entitlement.
When you re-install or upgrade Windows 10, it contacts the
Microsoft server, with the details of your tablet, and it
figures out you'd already received the Windows 10 Upgrade.
So it activates again. It doesn't need a local key for the
purpose.

If you buy a box of Win10 at retail, it actually comes with
a key, then the key in the Registry is unique and extractable
like any other Windows OS. But for the Win10 free upgrade,
the key in the registry is bogus, and the real key
is stored on the MS Activation Server as a "digital entitlement".

As for key storage, note that you cannot search for
xxxxx-xxxxx-xxxxx-xxxxx-xxxxx in a registry search. Like,
if you had the key in hand, and you were trying to verify
it was stored in the registry. It's actually in an encoded
form. It's not encrypted, just encoded. That is intended to
make it hard to search for. People have written the (trivial)
algo to convert that registry key back into the 25 letters.
So when you use a MagicJellyBean or whatever, it has a
copy of the algo to do the extract. The details of the
algo were posted, so you could eventually track it
down if you're curious. It was just a dumb thing for
MS to do, but it fits into their general approach of
how to design stuff.

Paul