Restoring your iPhone to its original factory settings can resolve a number of operating issues you might be experiencing with your device. If your iPhone is slower than usual, frozen or unresponsive, chances are a restore will correct the problem. This process is quite simple, however you will first need to back up your device and this can take up to an hour or longer.
Download iTunes onto your computer. You will see the download option on the main page of the iTunes website. If you already have iTunes make sure you are using the newest version.
Launch iTunes once the download is complete.
Connect your iPhone to the computer using your USB cable.
Click on "iPhone" under "Devices" in the options menu on the left side of the page.
Select the "Summary" tab at the top of the page.
Click on "Restore." You will see this option in the second box from the top, under "Version."
Click on "Back Up" when asked if you would like to back up your settings before restoring the software. This might take up to an hour or longer.
Select "Restore" when asked if you are sure you want to restore your iPhone to its factory settings.
Click on "OK" when you see this message: "Your iPhone has been restored to its factory settings, and is restarting. Please leave your iPhone connected. It will appear in the iTunes window after it restarts." Keep your iPhone connected until you see the message "iPhone is activated" on the main screen of your device.
Click on "Set up as a new iPhone" if you would like the factory settings to remain. You will see this option during the activation process after the restore. If you want all of your data to be re-synced to your iPhone click on "Restore from back up of" then select the drop-down menu and select "iPhone."
Restoring your iPhone will delete all of your music, videos, applications, pictures, contacts, calender information, notes, settings and any other data you have added. For this reason it is crucial you back up your iPhone before restoring.