How to find and remove duplicate items in your iTunes library

Choose File > Display Duplicates to show duplicate items (matches are based on the song name and artist). If you have multiple versions of the same song (for example, live and studio versions, or versions from different albums) you can hold the Alt or Option key (for Mac OS X) or the Shift key (for Windows) and …

Start/Restart the Apple Mobile Device Service (AMDS)

Symptoms If an iPhone, iPad, or iPod touch is not recognized in iTunes on Windows, the Apple Mobile Device Service (AMDS) may need to be restarted. Alternatively, you may see the following error when connecting your device: "This iPod cannot be used because the Apple Mobile Device Service is not started."