I am writing this for someone else. Please advice. The laptop in question is an HP ENVY, the OS is WIN10. NO CD's available. Is it possible to downgrade from 10 to 8.1? Will a cd work? More complicated than that? I can run the CD's as long as the machine lets me. Wifi connection. We are both stumpped. Can a third party do this provided he copies files onto a thumb drive or convetional hdd?