How to Get iTunes to Recognize Your iPod
If the icon for your iPod doesn't appear in iTunes when you connect your iPod to your computer, you can't synchronize the device with your iTunes library. This means you can't get your latest music and video purchases. However, if the iPod is functioning normally, get iTunes to detect it by performing a few basic troubleshooting steps.
Check if the iPod is recognized in other areas of your computer. In Windows, from the "Start" button, select "Control Panel," "Hardware and Sound" and "Devices and Printers" to see if the iPod icon appears. On your Mac, check your Finder for the icon.
Check the physical connection. Sometimes a port fails or an iPod doesn't seat fully into a connection. Remove the iPod and re-attach it. If it still doesn't appear in iTunes, check the cable connections and re-seat them if they are fully attached. If you are using a third-party cable, Apple reports that these cables may fail. Use the cable that came with the iPod or purchase a new one from an Apple store.
Disconnect competing devices that use USB or FireWire connections. Then reconnect your iPod to a USB connection.
Restart Apple Mobile Devices in Windows 7. Quit iTunes and select the "Start" button for Windows. Search for "Services" in the Start Search Field Type. In the list of programs, select "Apple Mobile Device." Select "Stop the service" and wait for
the program to cease. Then select "Start the service." Open iTunes and re-connect your iPod.
Charge the iPod fully. An iPod with a low or dead battery cannot synchronize with a computer. If the battery is too low, the screen may display an image of an empty battery or the message "Please wait, very low battery." The battery can charge from the computer's USB port; leave it connected for several minutes, and the icon will appear in iTunes when the battery charges.
Verify that your Mac can support your iPod. Review the system requirements for Mac and iPod to ensure that your computer can synchronize with your iPod (full link in Resources)
Download and install the latest version of iTunes if your computer does not recognize a new iPod. An older version of iTunes may not have the ability to detect a newer iPod model.
Restart the iPod. On an iPod with a click wheel, flip the Hold switch at the top of the device to both sides and then hold the "Menu" and center buttons on the click wheel until the iPod restarts. Reconnect the iPod to your computer and try again.
Disable your computer's anti-virus program and firewall and connect the iPod again. In some cases, a security program can prevent iTunes from detecting an iPod properly. If this resolves the issue, contact the manufacturer of the security software for support.Source: ehow.com