I don't see why not, as long as the license for that key matches the OS. A friend of mine used to buy COA stickers from eBay that had XP keys on them for like

I don't see why not, as long as the license for that key matches the OS. A friend of mine used to buy COA stickers from eBay that had XP keys on them for like $10 each. They are OEM keys so he used an OEM XP CD-ROM to install them with the keys on used systems. They would activate even if they have been used before. If activations run out you can call Microsoft and have them reset. Windows 10 Keys are different, locked to the hardware. Windows XP keys can be transferred to a different system.