How to Fully Back Up My iPhone
If you use the default, automatic syncs in iTunes, your iPhone is automatically backed up each time you connect it to your computer. If you have decided to manage the sync settings manually, iTunes will only back up your iPhone when you click the sync button or if you update your iPhone software. To back up your iPhone at any time, you can also select the "Backup" option. To fully back up your iPhone, you should store a copy of a recent backup on a CD or flash drive, stored away from your computer.
Plug your iPhone into your computer with its USB cable.
Open iTunes if it does not open automatically.
Select your iPhone in the "Devices" section of iTunes. If you do not see an entry for your iPhone, click the triangle beside "Devices" to reveal it.
Right-click on your iPhone. Then select "Backup" from the drop-down menu.
Wait for iTunes to back up your iPhone. This may take several minutes, depending on how much data you have on your iPhone.
Locate your iPhone backup file in Explorer. In Windows 7 and Vista, it can be found in your username file by clicking "AppData," "Roaming," "Apple Computer," "MobileSync" and then "Backup."
Copy the "Backup" folder to a CD or flash drive in case of a hard drive failure. In case of fire, store the backup in a location away from your computer and iPhone.