My computer originally came with Windows 10 preinstalled.
As I prefer to run Linux, but still need to use Windows for some tools, I have installed Windows via VirtualBox.
When I install Windows in VirtualBox, it asks me for the Product Key for activation. As this is injected into the BIOS and the virtual machine doesn't have access to the BIOS, I need to fetch it from the BIOS and enter it manually.
It can be fetched with the following command:
sudo strings /sys/firmware/acpi/tables/MSDM