I got ENVY m4 pre-installed with Windows-8 and it got upgraded free to Windows-10. I did system recovery 3-days ago and also purchased Office 365. I am getting regular pop-ups to activate windows. Contacted MS suppprt who said that I need to get the key number for windows-8 from HP as it is pre-intalled product. There is no key number in rear of the system , except for the sticker of windows symbol in the rear. How do I resolve this.