Put the device in recovery mode
How to perform a recovery-mode restore
If your iPhone, iPad, or iPod touch is already showing the "Connect to iTunes" screen, please go to step 5.
- Connect your USB cable to your computer but not to the iPhone, iPad, or iPod touch until step 3.
- Turn off the device: Press and hold the Sleep/Wake button for a few seconds until the red slider appears, then slide the slider. Wait for the device to turn off.
- If you cannot turn off the device using the slider, press and hold the Sleep/Wake and Home buttons at the same time. When the device turns off, release the Sleep/Wake and Home buttons.
- While pressing and holding the Home button down, connect the USB cable to the iPhone, iPad, or iPod touch. The device should turn on.
- Continue holding the Home button until you see the Connect to iTunes screen. When this screen appears, you can release the Home button:
Note: If the image of a battery appears, let the device charge for at least ten minutes to ensure that the battery has some charge, and then start with step 2 again. If you don't see the Connect to iTunes screen, try these steps 1 through 4 again.
- iTunes should automatically open and display the following message:
"iTunes has detected an iPhone in recovery mode. You must restore this iPhone before it can be used with iTunes."Note: If iTunes not open after two minutes, please open iTunes yourself.
- Use iTunes to restore the device.
A week ago I had the same problem when updating my iPhone 4 into iOS 7. I solved it by connecting my iPhone in a different computer that had iTunes in it. You just have to follow the steps normally and when it gets to the point where your iPhone tells you if you want to start as a new iPhone or if you want to sync with the security copy, is in here that you have to disconnect your iphone and plugged it in the computer that you normally use when adding stuff to it.