Not a gut feeling. If "OEM" is in the Product ID string then it is either factory or builder's OEM activated, or an illegal cracktivation.
It can't be Factory OEM if it isn't the licensed OS on the COA sticker.
It could be Builder's OEM if the uncle bought that instead of Upgrade version. I would ask him. Don't tell him why you're asking. He should at least remember whether he bought Upgrade or OEM version. If he insists its Upgrade then it likely means he or whoever installed cracked it.
A cracktivation is likely done at the BIOS level using a factory OEM key to emulate SLP factory activation like it comes from factory. I would wipe the HD first with Clean Command before any install: How to Clean or Clean All a Disk with the Diskpart Command