- Is the Windows activation key unique? (The Windows Product ID, I was told, is not.)
- Is it subject to change? And how about a clean install?
- Am I correct that that is what is found (encrypted) as
Yes the Windows Product Key you enter during Installation is stored as a digital product ID in that registry location.
It can be converted back to the product key
or if Windows is still bootable use a keyfinder program to recover it.
If you use factory recovery media made for your PC you will not need a Product Key (Dell, HP, etc), it will install one automatically and pre-activate the OS. These are called Volume Licence Keys and are different than the one printed on your COA sticker, a recovered/converted VLK will not work for manual installations when you use other install media than what was supplied with the PC.