A vehicle-mounted information processing apparatus such as a car-navigation system detects that a key switch of the vehicle has been set up at a Lock position (i.e., the engine is stopped). After that, the apparatus performs data reproduction of data files in an order from the oldest, then re-recording the reproduced data files with no change added thereto. Here, the above-described data files, which are stored within a magnetic disk device built in the apparatus, have been not updated for a constant time-period. This re-recording prevents a data loss caused by a thermal decay in the case where the magnetic disk device is mounted inside the vehicle that is likely to have existed under a high-temperature environment for a long time-period.