A method of providing error information to an outside of a hard disk drive, the hard disk drive, and a data processing apparatus therefor. The hard disk drive includes a first interface unit transmitting data reproduced from a medium to the outside and receiving data to be recorded on the medium from the outside, a hard disk controller controlling data to be recorded on the medium or reproduced from the medium and providing the error information including a type of an error occurring in the hard disk drive, a state information manager managing the error information provided by the hard disk controller and state information indicating operation conditions of the hard disk drive, and a second interface unit outputting the error information and the state information provided by the state information manager to the outside when the error occurs.