When troubleshooting your iPod, it is sometimes helpful to put it manually into disk mode.
Steps
Method 1 of 2: Using an iPod with the Click Wheel

Step 1. Before you put your iPod into disk mode, you must make sure it is charged

Step 2. Toggle the lock switch on and off
Set it to the locked position and then unlock it again.

Step 3. Press and hold the Menu and Select buttons for at least 6 seconds until the Apple logo appears

Step 4. When the Apple logo appears, release the held down buttons and immediately press and hold the Select and Play / Pause buttons until the Disk mode screen appears

Step 5. Connect your iPod to your computer
The screen on the iPod will change to show “Do Not Disconnect”.
Method 2 of 2: Using an iPod without the Click Wheel

Step 1. Before you put your iPod into disk mode, you must make sure it is charged

Step 2. Toggle the lock switch on and off
Set it to the locked position and then unlock it again.

Step 3. Press and hold the Play / Pause and Menu buttons until the Apple / iPod logo appears, then release the buttons
This will restart the iPod. Upon reboot, all music and data will be retained, however some settings may be lost.

Step 4. When the Apple logo appears, immediately press and hold the Back and Forward buttons until the Disk Mode screen appears

Step 5. Connect your iPod to your computer
The screen on the iPod will change to show “Do Not Disconnect”.
Advice
- If you're having trouble getting into disc mode, place your iPod on a flat surface. Make sure the finger that is pressing the Select button is not touching the Click Wheel. Also, make sure you press the Play / Pause buttons towards the outside of the steering wheel and not in the center.
- If you are still unable to put your iPod from the Click Wheel into disc mode, use your finger on one hand to press the Center button and your finger on your other hand to press the Play / Pause button.