My experience with versions of Windows has been requiring a clean install when going from 32-bit/x86 to 64-bit/x64 and that the Product Keys did not interchange between the two and not between Home and Pro. Didn't work much with Win8/8.1 but with Win10 the upgrade will be the same as what came with the machine, Home to Home, Pro to Pro.
I (too?) found you could not "upgrade" to Win 10/64 bit if you were running a computer with Win7 or 8.1 in 32 bit. I HAD to do CLEAN INSTALLS (on 2 computers) that were running Win 8.1/32 bit: if I TRIED to "upgrade," got the message "This computer can not run Win 10." A clean install to a new (or new SSD) allowed Win10/64 to install. While it HAS been over a year ago, I WAS able to use the Win 8.1 Pro license keys (legitimate, but already used for Win 8.1) to install and activate Won 10 Pro with a "digital license." Microsoft MAY have changed their policy now about use of Win 7/8.1 keys, however) to activate Win 10.
Win 10 home was always able to be upgraded to ONLY Win 10 Home; Win 10 Pro ONLY to Win 10 Pro. Win 7 Pro or Ultimate would upgrade to Win 10 Pro, as would Win 8.1 Pro. Win 7/8.1 Home editions would ONLY be upgradable to the Win 10 Home Edition. Good luck.
This is well known.. in general.I (too?) found you could not "upgrade" to Win 10/64 bit if you were running a computer with Win7 or 8.1 in 32 bit.
It was easy to move to Windows 10. However, only the following upgrades were free:
#1: Windows 7 Home Premium (32-bit) > Windows 10 Home (32-bit)
#2: Windows 7 Home Premium (64-bit) > Windows 10 Home (64-bit)
#3: Windows 7 Pro or Windows 7 Ultimate (32-bit) > Windows 10 Pro (32-bit)
#4: Windows 7 Pro or Windows 7 Ultimate (64-bit) > Windows 10 Pro (64-bit)
The following were also free but the intermediate step of installing Windows 7 (64-bit) required a clean install:
#1: Start with Windows 7 Home Premium (32-bit)
a) Clean install of Windows 7 Home Premium (64-bit)
b) Free upgrade to Windows 10 Home (64-bit)
#2: Start with Windows 7 Pro or Ultimate (32-bit)
a) Clean install of Windows 7 Pro or Ultimate (64-bit)
b) Free upgrade to Windows 10 Pro (64-bit)
Notes:
#1: If you wanted to go from Windows 7 Home to Windows 10 Pro you had to buy a new Windows 10 Pro license.
#2: The free upgrades from Windows 7 or 8.1 to Windows 10 ended in September 2023. Now if you want Windows 10 you have to buy a new license.
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