computer problem...volume lost..

[Box and one]

I recently lost my volume on my computer.The speakers work because I can play a CD on it.
Don't think it has anything to do with the mute.
I double clicked volume and a grey screen appears.
On it is master volume-wave-sw synth- line-PC speakers,etc
The balance and volume are all up and the mute is not on.
Can someone take me step by step to see if I can get it back.
Thank you...

 

[KMA]

Start with the easiest first, click on the little speaker in the right hand corner, it has a volume control as well as a mute button.

 

[KMA]

Did this problem just appear??? Have yah tried rebooting???

 

[Box and one]

KMA,I tried re-booting.When I right click the volume I get volume control.Click that and I get a whole bunch of things like adjust audio,properties,etc.I don't want to hit any of those???
If I left click the speaker I get the Volume and mute. Thanks for helping me.