Change Devices preferences in iTunes on PC
In the iTunes app on your PC, use the Devices pane in iTunes preferences to view and delete device backups, choose syncing options, and more.
To change these preferences, choose Edit > Preferences, then click Devices.
Displays a list of backups of devices that are synced with this computer. Encrypted backups are identified with a lock icon. Position the pointer over an item in the list to display the device’s serial number.
Delete the selected backup. All backed up files are deleted and can’t be recovered.
Prevent iPods, iPhones, and iPads from syncing automatically
Prevent devices from automatically syncing with this iTunes library when a device is connected. To sync a device, click the Sync button when the device is connected.
Warn when data on this computer will be changed
Be warned when syncing to a device will change a designated amount of data on your computer. Use the pull-down menu to choose the amount of changed data that will set off a warning.
Forget All Remotes
If you used the iTunes Remote app to pair an iPhone, iPad, or iPod touch with a specific iTunes library, select this option to disconnect all devices from that iTunes library.
Reset Sync History
If you’re having trouble syncing your iPhone or iPod with iTunes, resetting your sync history might solve the problem. Selecting this option won’t delete any synced information, but the next time you sync, you may be asked to merge or replace information.