Figure 1: Disk scan icon
This is a normal part of how iPod works. Built-in diagnostic software checks the hard disk for damage and attempts to repair it if necessary. If iPod finds an issue when it is turned on, it automatically uses internal diagnostics to check for and repair any damage to the hard disk. The screen in Figure 1 provides a status of the scan process, which can take 15 to 20 minutes. The magnifying glass represents the diagnostics taking a closer look at the hard disk.
When the diagnostics are complete, one of five screens appears. Each indicates the result of the test and the condition of the hard disk.
Figure 2: Disk scan failed and will be repeated the next time you turn iPod on or reset it.
Figure 3: No issues found.
Figure 4: Scan found issues with the hard disk, but was able to correct some or all of them. You should restore the iPod using the iPod Software Updater application.
Figure 5: Scan was canceled by user (by holding down the center button for approximately three seconds.) The scan will be repeated the next time iPod is turned on.
Figure 6: Surface scan was not able to recover the hard disk data. In this situation, the iPod requires repairs, which you can arrange at the iPod Service Web site.
If the Disk Scan Icon still appears when you turn iPod on, put iPod in disk mode and restore it as explained here.