Lost my windows product key and the hard drive is dead , and this has no cd : How do I recover?

I had windows 7 Professional ruing on this machine. I got this machine from my attic, but the key and Cd are lost. The HDD died a while ago and doesn't get detected in the BIOS. Is there anyway of getting the product key so i can install Windows ? Currently I am ruing ubuntu 16.04 live from a USB key.