a plea for pc help!

[saturn]

I've been trying to watch a video file on my computer and something's wrong with the sound. I'm getting video but no audio. I tried some other files and I'm having the same problem.

Nothing's on mute but, when I went into "Sound and Audio Devices" in the control panel I saw this.

Should that be grayed out? If not, does anyone know how I fix it? And, if that's not the problem, can anyone offer suggestions?

Assistance is greatly appreciated.