@Tuvok
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The licence key sticker was included.
However, as they had massed produced the laptop the installed version did not have the same licence key as stated on the sticker.
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I accept the truth of your account of what transpired but something wrong has happened there. If you buy a mass-produced "OEM" computer, the sticker on it should, nevertheless, carry a serial number which is *unique* to that box.
It should have hologram-like irridescence to parts of it and complex anti-counterfeiting graphics, like a banknote.
If it looks like a photocopy of a hologram/banknote then it has to be phoney.
Another possibility is that the sticker on the box relates to the version of Windows installed *at the time the hardware was first sold*. Could have been Vista. Could have been Win XP. Whatever the situation, it was evidently not the edition of Windows installed on the machine when your neighbour came to you for assistance. Those labels are firmly glued on and I'd rather leave it in place than have an ugly, scratched, mess where it used to be.
As general advice to anyone, if you are buying a computer second-hand, you should try to get the vendor to part company with the Windows Master disks, ideally, still with the original box, which carries the counterfoil to that serial number sticker.