it seems that you have deleted the asus back partition, you're just showing us the Windows gpt partition, (boot, recovery and os).as i have deleted the asus partition after i did the back up, i don't remember the capacity but my usb backup key is 13....
create an USB restauration key was the first thing you were supposed to do, there was a message that appears when you log on at the beginning.if you by-pass this step, i hope you didn't low level format your hard drive and you still have the asus bac...
it work like it's supposed to do, i also try to turn it off and on with the différents options in maxx audio and still ear the difference if i change the level of the Sub and still working if a change the level from MaxxBass from 0 to 100
i don't understand what is the PB ?you want to return on W8.1, so just put your USB key you made with Asus Backtraker and boot on it.it will format your harddrive and install all the software like it was when you bought it.
i've already gave the link here:https://rog.asus.com/forum/showthread.php?83222-Maxx-ROG-Software&p=575409#post575409the search option is your friend.but it won't change anything if your sub doesn't appear like in my screenshot