My laptop (Sony, Vaio) had Windows 8.1 version while buying. Later I chose to format it and install windows 7 ( which lasted for 30 days only). Now I would like to install or go back to original version which I had before but I do not have any product key for Window 8.1. The windows 7, I installed is just trial version. How can I get the product key for my computer or get back to original version of the laptop. Thank you Kindly.