I was wondering if I could use my serial key to go back to Windows 8.1? I upgraded legitimately from Windows 8.1 to Windows 10 and now I will be installing a new hard drive and starting from scratch because my hard drive is bad. However, I do not like Windows 10 for a ton of reasons and wish to go back to Windows 8.1. Is it possible to use the key that automatically activated Windows 10 when I upgraded from 8.1 to 10 for 8.1 again? Sorry for this question if it has been answered already. Thank you for your help.