sound stops working sometimes.

Okay a couple of weeks ago I posted about a problem with my laptop. The sound stopped working and I couldn't get it back unless I restarted my computer. I fixed this problem when I found a program that regulated my sound had a default power saver setting to shut off the speakers if my computer didn't have a sound event for thirty seconds. this is an astoundingly dumb feature in my opinon. Now the same problem is happening on my sister's laptop, but I can't find any program or power saver options that mess with the computer's sound outputs. I've checked the drivers related to her sound devices and they are up to date. So what can I do to help her. She has a laptop running windows 8, 2.5ghz processor, 4gb RAM, realtek high def audio. I've tried to use the test feature on her computer to test the speakers, but it says (even though the sound is inactive) that the speakers are being used by another application. I don't know how to find what application is still supposedly running in connection to the speakers, and don't know how to stop it as simply stopping it could fix the problem. So hopefully I can find some help here. thank you for your help.