Since Microsoft doesn’t keep a record of purchased product software keys, the onus is on you to figure it out. The good news is that the key can be retrieved from Windows 11/10 installation if ...

One method is to enter 'wmic path SoftwareLicensingService get OA3xOriginalProductKey' in Command Prompt This article ...

It comes programmed into your PCs. This embedded product key is stored in the NVRAM of the BIOS/EFI on the motherboard. It allows a user to re-install Windows on that PC any number of times.