My present computer which has Windows 10 purchased from the Windows shop.
I want to replace my motherboard and i5 processor for a faster i7.
My question is can I install the Windows 10 that I had onm my i5 computer or will I need to purchase a new Windows 10 to remain legal?
Walter
Legally you need a new licence, as original licence was oem.
However, Windows 10 from 1607 onwards do now have a facility to link the digital licence to MS account if you are logging in with an MS account. This was introduced to enable reactivation in event of failure to do so after a hardware change.
This permits digital licences to be transferred from one device to another a limited number of times, even if original was oem.
This facility was introduced after the EULA was written, and it has not been updated, MS certainly did not specify any specific restrictions when they brought out the transfer facility.
So in the end, it is really a matter of your personal moral conscience. I neither encourage or discourage you as to what to do.
How do you know he purchased an OEM Windows? Windows purchased from Microsoft via the Store App in Windows 10 would not be OEM, it would be retail.
@WalterW,
If you purchased your Windows 10 directly from Microsoft, then I would suggest that you use the method Microsoft has provided for transferring the license to the new computer:
https://support.microsoft.com/en-us/help/20530
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