You may wish to try plugging it into your computer, opening up the Disk Utility app, and see if it shows up in the left hand pane. Go from there - it may be a software issue. My 80 GB 5th Generation iPod Classic showed a dead screen, and now I'm getting a faint 'Please wait - Very low battery' issue on the screen, so it's probably my battery, although I've basically only used it as a storage device - go figure.