sound suddenly gone

I've suddenly lost my sound. Can anyone help?

operating system please
what windows version?
do headphones work of plugged in?

dx

I don't have headphones. windows 7. 64 bit operating system.

and is this a laptop or desktop pc?
if its a desktop
if you unplug the little plug that goes into the back of the pc to your speakers
do they make a buzz or a crackle as you pull the plug in/out then back it?

are you speakers turned on if they plug into the mains too?

dx

thanks to those who tried to help, but it seems like my tower has gone to computer heaven.