stay away from SpeedMaxPC you don't need it. It's 'Free to try (Free scan, fix-disabled) $29.99 to buy' According to the reviews and other forums 'Anything it purports to 'fix' can be fixed in a safer and Free way' Also it finds problems that don't exist.
I lost my sound having had to unplug all the cables and had probably put all the audio ones back in the wrong place (by mistake). My Realtek on-board audio is supposed to manage this but obviously got itself in a muddle. Had to call in my local guru who, having gone through all the usual checks downloaded the latest driver from the Realtek site. Magic, all is well. So the advice from Chronos is probably spot on.