Have you tried resetting it by pressing and holding the home and power button for several seconds?
Is iTunes recognizing it?
If iTunes doesn't recognize it, put it in DFU mode and then restore in iTunes.
Do you know how to put it in DFU mode?
plug it into you computer then hold the home and power buttons until the phone turns off then release the power button and continue to hold the home button. iTunes should recognize the phone.
iTunes will say phone is in restore mode but your screen should be dark. this is DFU mode.