My iPhone wont connect to either iTunes or my computer

Hi my name is Connor recently my iPhone 4 has stopped connecting to my laptop or iTunes! i have tried about 4 different usb leads to see if that was the issue but all of them dont connect it. It makes the noise that it makes if it connects but it hasn't connected. my laptop is running windows 7 and its a dell laptop. i also have a ipad but that connects fine.. i cant figure it out please can someone help!!

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