I was given this pc as broken,even though everything works. I recovered it,fixed it,cleaned it.It was working fine but i had to downgrade it back to windows 7(i had installed windows 10,and they had already done a clean install of windows 7, meaning that no recovery programs or drivers were left). again it was working fine and i left it for a couple of months.last week i opened it again just to play with it but no sound coming.I tried everything from easy things like letting windows find the problem to installing modded drivers but no luck.i checked if the connections are ok and they are. there is sound on the bios since i can hear beeps. Please help. My laptop is an hp compaq presario cq71 410ed