Just so you understand(I realize reading a post is not the same as hearing it verbal) I wasn't trying to be snooty.
I keep all my keys, Windows and 3rd party, in a folder, synced to all my systems on OneDrive, and in a backup of my libraries on an external HDD, that sits in my closet, plus written down in a little green book.
For such important data there is no such thing as enough redundancy
You obviously do not understand how the free upgrades work.
This tip is absolutely no use for free upgrades, as the product key is only a generic one.
You get a digital licence tied to the hardware id and this is registered with MS and you do not even need a key to reinstall.
Yes. You can (and I have) put a new HDD in a machine that's previously had the free upgrade activated, do a clean install and the activation servers will activate it automatically. Microsoft are on record as saying:“For Windows 10, we have factored out the hard drive in regard to licensing,”
If you get asked for a key while installing, just click 'I don't have one' to carry on.
Also if you sign in with your Microsoft account, the digital licence is also tied to your Account in addition to your hardware ID.
This, it has been stated, By Microsoft, is capable of re-licensing a Windows 10 system where the motherboard had "died". No mention has been made of this not applying to OEM systems so it may be worth doing this by default even on these systems which are not normally recoverable if a Motherboard died.
You have to have AU 1607 installed of course, but yeah - this is interesting as oem is a grey area. According to EULA, it is not permitted to transfer digital licence but I am certain the digital licence carries no history of its origin ie you have one or you do not - no retail or oem distinction.
My conclusion is that MS had to produce a tool to allow users who upgraded from retail windows 7/8 to be able to transfer digital licences to comply with their own EULA. In the free period, this was not an issue. However, I think any digital licence can be transferred as MS do not have any way of knowing if original was retail or oem.
A second conclusion is MS probably do not really care as the number of people this pertains to is a drop in the ocean compared to total number of installs. It would probably cost far more to put rigorous checks in place than the minor revenue loss.
I think all MS care about is keeping people on the W10 ecosphere. I think this is borne out by the fact that there does not seem to be any time limit any more on running unactivated versions of Windows 10 either.