A vehicle navigation system is composed of first and second recording devices, first and second execution modules, and an install module. The first and second recording devices respectively store therein first and second computer programs used for vehicle navigation. The first and second execution modules respectively execute the first and second computer programs. The install module transfers data stored in the second recording device, including the second computer program, to the first recording device. The install module is allowed to operate during operation of the second execution module, while the first execution module is prohibited from operating during operation of the second execution module. The second execution module executes the second computer program by using transferred data which are transferred from the second recording device to the first recording device.