problem occurs after downgrade to win 7 ult

hi,

I just downgraded my pc from win 8.1 to win 7 ultimate. after successfully downgrade. There are some changes occurs. For example : When I press volume button from my keyboards it does not appears volume bar at screen layout and others bar as well, which was working fine in win 8.1. How it would be work?

Note that I already installed all the drivers from dell site.

thanks