How can I restore sound on my PC?

Ok, I have an Acer desktop computer, that was given to me by a friend. When I set it up, I noticed that the sound coming through the speakers was really tinny. I tried to do my best to adjust the sound, but to no avail. So, I just lived with it. Recently, my wife tried to fix the sound herself. And she made her own adjustments and now there's no sound at all. No matter what I do I can't figure out a way to bring the sound back. Is there anyone out there that might be able to help? Thanks.