Beginning with Windows 8 and Windows 8.1, you may have noticed that there is no longer a sticker on computers or laptops that tells the Windows product key. Microsoft hopes to have fewer compromised keys by making them less obvious even though manufacturers were getting pretty good at hiding them under batteries or other removable slots on laptops.
Alternatively, OEMs like Dell, HP, Lenovo and others are storing the product key in the firmware/BIOS themselves. There are a few methods to retrieve the product key if you need it for inventory or backup purposes. If you replace the hard drive and need to reinstall Windows, the Windows 8/8.1 setup will actually read the product key from the motherboard, so you don’t even have to type in the product key. However, if the motherboard had to be replaced, you might want to retrieve that information before it is too late.
If you are currently running Windows 8/8.1, you can run Nirsoft’s ProduKey to retrieve the product key from the registry.
Alternatively, if you have downgraded to Windows 7, you can run this compiled python script on Github to read from the motherboard.
And last but not least, you can read all the information you would like and more from the BIOS with RWEverything, a utility that can access the firmware and display information. If you hit the ACPI button and switch to the MSDM tab, this will show you where Microsoft stores the product key. The key will be displayed twice, once next to the binary data and then below with a little better formatting.
RWEverything can be installed or is available as a portable app. The portable x64 version is a 4MB download and a 13MB portable app when extracted.