Sound not working OSX 10.6.8

I was backing up my documents and older files on to an external hard drive and noticed that the sound has disappeared from my Macbook pro. I have OSX 10.6.8 Does anyone have any tips on what to do?

Is there any file to make the sound work

I've tried a few tricks mentioned on line, but no luck (also cant see any options in the sound for output and input devices - in system preferences)

My mic and headphones both dont work!