Your iPhone stores your personal calendar information, contacts and email data. In order to prevent the loss of your iPhone information, iTunes creates backups every time you sync your iPhone to your computer. These backups are used if you restore your iPhone to factory settings. iPhone backups are stored on your hard drive and are viewable in their folder or through iTunes. After your iPhone is restored, you select your backup from a list and that data is restored to your iPhone.
In order to restore your backup to your iPhone, you must use iTunes. The option to use the backup is presented at the end of the restore process.
Open iTunes on your computer.
Open the “Edit” menu. Select “Preferences” from the list. Click the “Devices” tab.
Browse your iPhone device backups. You can view the date and time of the backup. Select the backup and click the “Delete Backup” to erase a backup.
Open the “Start” menu. Open your user folder in the left navigation pane.
Double click the “AppData” folder. Open the “Roaming” folder.
Double click the “Apple Computer” folder. Open the “MobileSync” folder.
Double click the “Backups” folder. This is where your backups are stored. Don’t delete any information if you don’t know what it is.
WTF! PC Help & Support: iPhone