The license key is included on the pre-installed operating system and in the image of the OS. If they were not kept in a USB drive or SD previously, it will be necessary to replace the compute stick.
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Thank you for your reply !
The license key is branded in the UEFI BIOS and i can get it out with some third party tools but the problem is when we use the image of a second Intel Compute Stick, the first one isn't activated anymore. the license key is the UEFI is still Windows 8.1 and the image is Windows 10. the original license key is not upgraded to windows 10 in this process and i'm wondering if its possible to do so afterwards.