Me too, have taken much time to make sure I don't have a software or hardware problem, (Acer 7741Z-4433 Windows 7 64bit) those avenues are exhausted and I also still have no sound: a couple weeks ago I noticed an exceptional amount of dis-engaged noises while the speakers were still working so know it is a mechanical problem.
I am looking for an external speaker or headphone to try the external connection. I suspect that will be affected as well. So, am saving all my videos and music recordings to another ex drive so I don't lose them when the rest of the systems fail!! Not optimistic in finding a solution.