How do I find the product key for Windows 8.1

Thank you for the suggestion.Vic!!!

Thanks for sharing your experience, HairyFool. As you said, all I can do is try then.

... but problem is, I have no confidence in that second "key" that got computed by a script I ran is even a valid key at all: it effectively just got a different registry key (DigitalProductId4) and applied a hardcoded transformation to it. This might be garbage-in-garbage-out kind of situation, since I am the one who tried to modify key location (from DigitalProductId to DigitalProductId4) and original script was just using DigitalProductId. So going back to my original question then...

• What's the best way to try to locate that potentially useful Win 8.1 Pro key without upgrading my Win 7 system? E.g. should I run some key finder on the system itself or try to scan the 8.1 Pro upgrade DVD for it?
• What software or technique wold you recommend for such a scan?

I appreciate your answers - very educational!

The problem is you are actually running Windows 7 as opposed to the operating system for the key. 7 which knows nothing about BIOS loaded keys is not going to know how to get it.

I use Produkey from Nirsoft. Running it on my Surface confirms a few points.

It reads the Windows 8 BIOS key although I am running Windows 10

The Windows 8 key has been applied as the license key for Internet Explorer as part of the upgrade to 10

Because Windows 10 uses a digital license system the 10 key is the one generated when you don't enter a key during setup (i.e. a new key is not generated even though it is fully licensed)

I think your GIGO suggestion is most likely.

Thanks HairyFool, I ran Produkey as you recommended, and found a BIOS OEM license key that I did not have before. It ends with xxxxx-xxxWMC. Any idea whether this looks like 8.1 Pro key and whether it's HP specific?

(E.g.  it could be potentially useful for an Acer upgrade from Win10Home to Win10Pro that they mentioned in the article I had linked. If it works, I would end up with running both Win7Pro on the original HP computer and an Acer Win10Pro using this other license... ?)

I would doubt it.

In much the same way as the factory build keys will only work on the right hardware for Windows 7 I would expect the BIOS keys to be locked in some way.

Windows 7 Manufacturer builds are pre-activated in that they don't have to connect to the Activation servers. Windows 7 DVDs are not and must be activated on line. If you enter one of the build keys in the setup dialogue when it then tries to activate it fails even if on the correct hardware. We have lists of the OEM keys but they are mostly used to identify hacked systems, as it can be seen when the hacking fails.

To be honest you are trying to discuss bypassing Microsoft licensing on a Microsoft site but they have the system fairly well locked down so its not going to be so simple as to read the BIOS key, something we have been able to do for some time. You are trying to run two systems having only bought one license, the fact that the Acer is an upgrade so has a licence is irrelevant as it would be the wrong one. You may now have two keys for your HP, the Windows 7 off the disk and Windows 8 from the BIOS but they are under either/or terms.

Being able to read the key in the BIOS is fine but personally I never found a use for it. I use the utility primarily to get the OEM Office key before a reload as most users have lost the keycard with it on.