Restore ipod but itunes wont recognise the ipod.

My ipod classic is in disk mode and has a circle with a line through it and it says do not disconnect. it has been this way for a while the circle with a line through it blinks and here is a syncing circle up in the left corner which appears and disappears but my iTunes on my computer freezes and doesn't pick it up when the iPod is plugged in. how do I get my iPod to work again?