Hard disk drives with CRC (Cyclic Redundancy Check) errors

What is CRC on hard disk drives ?:

During data transfer between hard disk & computer (for example when a file is opened, or data is saved to the hard disk), a technique known as CRC is used to ensure the non-corruption of this data during transfer. If an error is detected, a CRC error is generated and the data is re-transmitted.

CRC errors on hard drives:

Drives that produce CRC errors frequently have difficultly reconciling the data received with the transmitted. This can be for a variety or reasons such as poor cabling, hard disk microprogram corruption, or electronic related problems

Data recovery from hard disks suffering with CRC problems:

The likelyhood of successful data recovery is dependent on the cause of the problem and how long the problem has been occuring. Recovery can be relatively simple for electronic related issues, to complex if microcode corruption is involved. Additionally, there are several malicious programs that will cause Windows to report CRC errors.

CRC application on hard disk drives:

The most common method of checking for errors after data is transmitted is by checking the parity bit of a byte or word that is transmitted. The sign of the parity bit detected at the receiver has to match that of the transmitter. If there is a mismatch, an error is flagged. Likewise, Cyclic Redundancy Check (CRC) codes can be generated for each data transmission, and these should be identical at both the transmitter and the receiver. Any differences imply an error has occurred during transmission.