How to Restore an iPhone or iPod Touch to factory settings
This video demonstrates the steps to restore your iPhone or iPod Touch to original factory settings. This is a way to undo or repair any damage to your phone caused by downloading unauthorized files or corrupt files. Be aware that this will delete all the files that are on your device including music, pictures, videos and contacts, so use this method when all others fail. First connect the device to a computer via USB and select the device in iTunes as shown. Go to the device's information page and click the restore button. Back up, save your data and wait for the restoration to complete. Start setting up your device as a new iPod touch or iPhone.