MY IPHONE IS AN OLDER VERSION (3G) trying to restore

MY IPHONE IS AN OLDER VERSION (3G) BUT HAS WORKED FINE TILL NOW. MY PROBLEM IS THAT NOW THE SCREEN DISPLAYS THE WHITE CORDED PLUG AND THE ITUNES SYMBOL AND WILL NOT ALLOW ME TO USE MY PHONE! I'VE TRIED HOOKING IT TO MY LAPTOP TO RESTORE,BUT WITH NO REsults