No sound on Advent laptop?

The sound that should come from my Advent laptop has dissappeared. I have checked and there is not a mute on and all the boxes in volume control are unchecked and the bars are at the top of each scale. I've looked for a website to get upgrades from but I don't know what particular model or type it is and there doesnt appear to be a website to begin with. I'm not a very technical person so I have no idea where to o from here. Please help me.