I'm afraid there's no Processor Serial Number in modern CPUs. I'm concerned about this (well, maybe 'concerned' isn't the right word) because I probably will not be using Windows 10 before 2020.
Yeah, they might have midified the listings from time to time, but as I don't have much interest in these things, so just copy from my archives.
I'm not sure, just it's simply possible that Microsoft will 'move' the Product Key of the 'old' OS from the used database to the new Windows 10 Database. In that case, if someone try to reactivate the old OS, that key wouldn't work any more and could only used further on with Windows 10. In such case, I'm not sure that Microsoft would use the Hardware ID as Identification because regarding the published information, User's could do an Clean Install of Windows 10 after the initial Upgrade from the Old OS to 10. On the end of the day, we still have to wait and see what really would be happen after July 29. 2015!
Boot manager is different in Windows 10. Will see later if the above trick still work for dual booting . I like it because you have quick access to all sub-menus with F8 key at boot. I don't use fast boot with SSD's , so my SSD is never flagged dirty at shutdown.
The original question was basically "Will my Windows 7 retail/OEM key work if I use it to upgrade to Windows 10?" and the answer to this question is an emphatic 'yes'. Microsoft would never cripple your Windows 7 product key after upgrading to Windows 10 - especially since there is no physical software that has been shipped out to the millions of people who will soon be running this operating system. If MS were to kill your old key just to activate your Windows 10 activation key sequence then they would be shooting themselves in the foot because you would not be able to recover your PC in the future should anything happen. Say your hard drive goes dead two days after you upgrade to Windows 10, and you haven't had the time or know where to download the ISO for Windows 10 and make your own installation media for safety's sake. You'd still have to be able to install Windows 7 AND activate it properly before you could start the upgrade to Windows 10...and it's that logic that proves that your Windows 7 key will be completely untouched and fully usable in any other computer should you choose. The legality of it all is a completely different story since your Windows 7 retail/OEM license will have been "confiscated" by upgrading to Windows 10 but the key will have been freed up to be used on any other computer should you choose to do so. In the real world you could take a single copy of Windows 7 Retail and install it on multiple machines, run the Windows 10 upgrade on the installed operating system, and then turn around and move your retail Windows 7 key over to a completely different system, install it, and upgrade again to Windows 10. I think the problem some people are facing is that they believe that Windows 10 is reusing your old Windows keys as their primary CD keys when in fact they're using generic KMS/VL-like generic keys tied to hardware IDs to fully identify and activate your system. Once your computer has been fully activated within Windows 10, there is no more link between your current installation and your old OS's activation key - it's just used against their server-side test to make sure that you are running a legitimate installation of Windows 7/8/8.1 prior to the upgrade.
I said in the other thread that after upgrading and then using rweverything to check it my bios key is the same as it was. I believe this verifies what MS says in that the key is consumed by the upgrade. You can still go back to your old OS on the same machine but I don't think you can move to a new one without phone activation assuming that still works in windows 10. They are giving you windows 10 for free after all and that's the price you pay, trading in your key. People seem to think they should just give it to you free and nothing with your old os should change at all..that's a good trick if you can pull it off.
After all the confusion and so many hoops, if I want to switch to Linux, will MS allow me to format the system. Frankly visually at least, the office 2013 visually incoherent interface has been transported to windows 10 with more confusion and mess carried along.
I'm sure you can format it and I'm sure you can come back to the same pc with either your original os or w10, you will just need an internet connection for them to verify it.
If take the info from MS by it's words, means we couldn't go back to the old OS! The Reality may differs?! That was exactly why I pointed to the change of Databases, moving the old PKey from the Old Database of W7 & 8.X to W10 would solve that and even Phone Activation wouldn't work anymore if you go back to that old OS! We'll have to wait a few weeks and then it could be tested!!
I would be already happy enough, if it would be at least possible to go back to 8.1 on the same PC / Base-Hardware after the 30-Day-Period, if I see that things don't work as flawlessly as expected. For a complete new build I would get a new Windows-10-License, because the hardware should be Windows-10-Certified by then.