Hello guys! I have a pc with windows 8.1 installed, the offcial ones... The store i bought my pc from , gave me a recovery cd which contains only a 4gb file.. it cant be full windows i guess...They didnt gave me a product key...I found my product key with a 3rd party software..Now I want to reinstall windows..Will this product key work, since its the same pc? If not what can i do?