The iPod has a special Disk Scan utility that can be used to check the hard drive. Follow these steps:
- Do a Reset – Press the Menu + Pause/Play buttons until the Apple logo comes up.
- At the Apple logo, press the REW, FF, Menu and “Action” (the center) buttons. The iPod will begin to go through a disk scan. At the end you will be presented with a Disk icon with a check mark or a sad iPod icon. If you get a sad iPod icon you need to send your iPod in for repair.
See this Apple article iPod: Disk Scan Icon Appears When iPod Is Turned On for an explanation of the various icons.