The only keys (Windows or Office) I've ever had were the ones that came with the used PCs that I bought, so upgrades were a necessity.
This particular XP I upgraded to Win10 was retrieved from the HDD of my trusty old XP laptop that had not only a Windows key, but also a licenced copy of MS Office 2003. When the laptop died the only remaining working part was its IDE HDD.
It sat for years in a draw, gathering dust. After Win10 arrived I took an image of the drive and restored it to a VM to do the upgrade(s). It then spent another few years waiting for an appropriate machine to put it on. It now lives on my little Acer AOD270 Netbook that's too old to run anything newer that Win10 or Win11 23H2.
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Enrolled in the Win10 ESU it has another year of useful life before the almost inevitable switch over to Linux....