Laptop came with original windows, you did something tricky to install linux – and resulted in removing your entire windows.
Boot into your Linux OS. If you dont have one, try making a linux bootable USB stick. In terminal,
sudo hd /sys/firmware/acpi/tables/MSDM
This would give your key on the right side of the hex-dump! Enjoy 🙂
Courtesy : http://malwaretips.com/threads/how-to-retrieve-your-windows-8-oem-key-with-linux.28560/