Also, I can burn the tech bench iso to a disk and boot into the new HD and install windows that way?
Edit: I got the product key! (or a product key, not sure if it's guaranteed to be accurate...)
This is an interesting test case.
Product Key: Retail license
Digital Entitlement: Upgrade ... activation information stored on MS servers
OEM (Dell, HP, Asus, etc): Key is embedded in firmware
So what does Adam have? A PC builder machine.
The first attetmpt as NovHak and simrick implied is to just try installing Win10 on the new HDD (or SSD).
Skip entering the key on the windows that ask - it will either activate or you cna add the key afterward the instal finishes
The two scenarios where Win10 will activate without entering a key during install are: OEM and Digital Entitlement
The only scenario where you would have to enter a key after installing would be a Retail product (probably includes OEM builder license).
Did you run Check Product Key in Showkey?
Does the result confirm your installed edition?
If so, then you're probably good to go ... not much more for me to offer ... good luck
To respond to this more directly; I wasn't able to get it with ShowKey, it said that there was no OEM in the firmware in the backup - I also tried running the executable from the bad drive, with the same result.
However, I did install Lazesoft software recovery suite to the bad drive (very slowly) and it has a password/key recovery option which is what gave me my key.
A good sign is, putting that key into Showkey does also give me the correct version.