Apple's iTunes software is a convenient management tool for the audio and video content on your iPod. Using more than one iPod with one version of iTunes can cause problems with an iPod, however, as the settings on the other iPod may cause all the files on the device to be erased when you sync the iPod with iTunes. Fortunately, this iPod setting is one that can quickly be changed through iTunes, allowing you to use the device with iTunes safely.
Open the iTunes program.
Plug the other iPod you want to use with iTunes into a USB connection on the computer.
Click on the iPod listed in the iTunes program underneath “Devices.” Once you do, many different tabs for that iPod will show up at the top of the program.
Choose the “Summary” tab to see the available settings for the iPod you plugged into the computer.
Click on the inside of the “Manually manage music and videos” box at the bottom of the program to put a check mark in that particular box.
Click “Apply” found at the very bottom of iTunes. You will now be able to use the iPod with iTunes without the program removing songs from the device.