To restore iPhone and reset the phone to default factory settings,
follow these steps:
1.Turn off iPhone
2.Press and hold down the Home button for about 10 seconds until a yellow triangle with a text which says Please Connect to iTunes appears.
3.Connect your iPhone with PC,
iTunes will prompt a message that says iTunes has detected an iPhone in recovery mode.
4.You will be taken to the iPhone pane.
click on Restore.
5.Wait for the full restoration process to complete,
and the iPhone will be back to the factory original settings.