sound icon

it disappeared from my taskbar on window 8.

Not sure if this will match Win8, but open the Control Panel and look for "Sound and Audio Devices". When you double click on that, you should see a page that permits checking "Place volume icon in the taskbar".
With my system it is on the Volume page.

That happens to me sometimes in Windows 7. It comes back when I restart my computer. Doesn't seem to hurt anything.

that is what i did, came back.