|Hi Muzzo, google is your friend in such matters.|
Google and HP do not appear to have any hits for hp pavilion a810r, however there are many for a810n.
Could this be your model? Here manuals can be found:-
Googling hp pavilion a810n motherboard, produces hits such as :-
This advises sound is integrated.
Could there have been a sound card fitted that required a stap setting ceasing onboard sound, or drivers been deleted, or bios setting changed?
Good Luck - Keep us posted.