[metacafe 318610]
This Metacafe video by kipkay [kipkay.com] shows us the inner workings of a computer hard drive. Basically, kipkay took apart an old hard drive and ran his PC to show us the spinning hard drive disk and the quick moving arm. The clicking working sound that you hear when your computer does a lot of processing mostly originates from the hard drive arm flicking back and forth as seen in this video.
Inside A Hard Drive! See What Goes On Inside… [Metacafe]