Awesome, thanks for the info. Recently I purchase a key (win 10 pro) and it works perfectly for first time. However when I tried to reformat my pc, the key cannot be used and cannot activate online. Until I decided to use activation via call and tadaa, the win 10 activate successfully. Some said when your pc is activate first time, you can save time by sign in to your microsoft account and let the windows sync the product key to your microsoft account. and if you need to format in future, you just need to sign in to microsoft account without need to key in or activate it back.