iPod Classic - Not Recognized
The iPod displays an image of a sad iPod when turned on
Sometimes, a reset and restore will fix a sad iPod. Connect your iPod to your computer and use iTunes to restore the iPod. Restoring the iPod will erase everything on it, so make sure everything on the iPod is stored elsewhere prior to restoring. Sometimes it may be necessary to restore the iPod several times before it works properly. If you are unable to restore your iPod using iTunes, you can hard reset your iPod. iPod Classics can be hard reset by booting while holding the menu and play/pause buttons. This should result in a quick dark screen followed by the standard Apple boot graphic.
Bad hard drive
It is also possible that the sad iPod icon is caused by a bad or poorly connected hard drive. If no information is being sent to the iPod from the hard drive, it makes the iPod quite unhappy! Note: Video iPods have unique connectors, and only specific hard drives will work in them. Browse our hard drives (thin or thick) and check out our iPod ID pagefor compatible drives.
Bad battery connection
Another potential issue is the battery's connection to the logic board (a bad battery should not cause this error, however). To test this, carefully detach the battery and re-connect it to the logic board.
Bad logic board
If restoring the iPod and diagnosing the hard drive and battery connection does not fix the problem, the sad iPod is likely caused by a problem with the logic board. There's not much to troubleshoot here. Basically, the only option is to replace the logic board.