Shortcut buttons for managing sound

Hello,
After cleaning my computer from viruses, I have erased by mistake one start-up program for managing sounds. Before I could easily press FN + Volume up/down/mute buttons on my laptop to manage sounds. However, since the clean-up, it does not work.
I assume the driver / start up program is missing.
Does anybody know what should I do?
Which program controls shortcut buttons for sounds?
Regards,
M

Laptop: ASUS A9RP series,
Sound card: Realtek HD Audio