Basically all the tutorial says is that you go to the notificatioan area and tick off the icons (volume icon) that you want to show.
Go to search by the start button and type notification to get started.
I have set that to show, but it has made no difference.
A system restore would probably do the trick, but I
would lose all the Windows updates as well.
Incidentally, ticking and unticking the volume icon in notification
area only affects the sound icon in the taskbar, not the volume indicator.
The volume indicator is usually a function of the keyboard driver, and appears when you press one of the volume keys (or the mute key) on the keyboard. As you correctly mention, the notification option only affects the icon in the system tray and not the volume level indicator. Sometimes, an seemingly unrelated update can cause this to disappear, even though the keyboard is still able to control the sound level as before. Bizarrely, it can sometimes reappear without having to do anything. Another thing that can happen is that the indicator can become out of sync with the volume status (i.e. show as muted when the sound itself isn't).
I've had this happen myself, but why I am not sure.