120GB classic ipod is corrupt

have you tried resetting the ipod?? to reset it hold down the menu button and the center button together

You will want to attempt to force the iPod into disc mode then restore using iTunes. With the iPod in disc mode, iTunes should show the iPod. You will have to restore the iPod to resolve the issue of corruption though. Please let me know if this does not resolve your issue. :)
Putting ipod into disc mode http://support.apple.com/kb/HT1363 Toggle the Hold switch on and off. (Set it to Hold, then turn it off again.) Press and hold the Menu and Select buttons for at least 6 seconds until the Apple logo appears. When the Apple logo appears, release the Menu and Select buttons and immediately press and hold the Select and the Play/Pause buttons until the Disk Mode screen appears.
Connect the iPod to your computer; the screen on the iPod will change and say "Do not disconnect" If you are having difficulty putting the iPod model into disk mode, set it on a flat surface. Make sure that the finger pressing the Select button is not touching the Click Wheel. Also make sure that you are pressing the Play/Pause button toward the outside of the Click Wheel and not near the center.
If you are still unable to put your iPod with a Click Wheel into Disk Mode, use one finger from one hand to press the Select button, and one finger from the other hand to press the Play/Pause button.
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How to restore iPod (ARTICLE NUMBER HT1339)
Open iTunes, and then connect your iPod to your computer using the USB or FireWire cable that came with your iPod.

After a few moments, your iPod will appear in the Source panel in iTunes.
Select your iPod in the Source panel and you will see information about your iPod appear in the Summary tab of the main iTunes windows.

Click the Restore button. You will be prompted with one or more restore options that may prompt iTunes to automatically download the latest iPod Software.

The 4 possible restore options are: Restore Option

1: Restore - Restores with same iPod Software version already on iPod. Restore Option

2: Use Same Version - Restores with same iPod Software version already on iPod even though a newer version is available. Restore Option

3: Use Newest Version - Restores with the latest iPod Software available. Restore Option

4: Restore and Update - Restores with the latest iPod Software available.

If you are using a Mac, a message will appear prompting you to enter an administrator’s name and password.

A progress bar will appear on the computer screen indicating that the first stage of the restore process has started.

When this stage is completed, iTunes will present one of two messages on screen with instructions specific to the iPod model you are restoring.
Restore Instruction 1: Disconnect iPod and connect it to iPod Power Adapter (typically applies to older iPod models).


Restore Instruction 2: Leave iPod connected to computer to complete restore (typically applies newer iPod models).

During the stage 2 of the restore process, the iPod will show an Apple logo as well as a progress bar at the bottom of the display. It is critical that the iPod remains connected to the computer or iPod Power adapter during this stage.

Note: The progress bar may be difficult to see since the backlight on the iPod display may be off.

After stage 2 of the restore process is complete and the iPod is connected to the computer, the iTunes Setup Assistant window will appear asking you to name your iPod and choose your syncing preferences similar to when you connected your iPod for the first time.

Try resetting your iPod a classic
Press and hold the Menu and Center (Select) buttons simultaneously until the Apple logo appears, about 6 to 8 seconds. You may need to repeat this step. Hope this helps