So here's my guess at how Windows 10 Activation will work:
My theory is that whenever windows 10 activates, it will 'phone home' to the activation servers with info about the hardware signature of the activated computer, and which edition has activated.
Every time you install windows 10 and it wants to try to activate, it will also 'phone home' with the current hardware signature to ask the activation servers if that hardware is a recognised device, and what edition it was running. If so, it will automatically activate with the recognised edition, without asking for a key, and in some cases there won't be a specific product key as we'd know it.
So some scenarios are:
- When Windows 10 is upgraded over Windows 7/8.x, it will perhaps check that the key on the running system is valid for 7/8.x, and then activate Windows 10 with the corresponding edition for that hardware
- When Windows 10 RTM is clean-installed on new hardware, it will check for a key on the motherboard, or that it is hardware that has activated before, or as a last resort ask for a key to be entered by the user, and then activate
- When Windows 10 RTM is installed as a paid-for upgrade on a box running something that is not Windows 7/8.x/10 , it will check whether it is hardware that has activated before, or ask for a Product Key and then activate
- When Windows 10 Preview is clean-installed (presumably requiring a recognised Microsoft Account), it will just activate, although I imagine this behaviour will stop on or before 29 July
- When you install a 'Pro Pack' (assuming it still exists) to upgrade from one version of 10 to another, you will type in the new product key and the information on the new edition and the hardware will be passed to the activation servers
So this behaviour which Mystere has observed would fit with the above (assuming Windows 10 had already activated on that hardware), and also suggest that 10147 is a release candidate or close to one, and perhaps that the activation servers are up and running for Windows 10.
The scenario I don't have a good theory on is when you change hardware. In some cases I imagine there will be some tolerance that if most components are the same as hardware that's activated before, then it still activates as the same device. But if you make major changes I'm not sure how it will work especially if, for instance, you clean-installed 10 Preview and don't actually have your own product key to give to a support person when you call Microsoft?
This might also be what the 'supported lifetime of the device' thing for the free upgrade from 7/8.x is about - if the hardware itself is effectively the product key, then if you make big changes to the hardware it may no longer be treated as valid, and you won't have a Windows 10 product key to give Microsoft when you phone them. If it is still 'supported' then the OEM should be able to sort you out with a new key if necessary when you replace/fix components.
Probably over-simplistic (it may be that Microsoft Accounts enter into the rules too) but that's my 2 cents...