A hard drive that is beginning to fail rarely fails cleanly. In most cases the user notices unusual noises, slow file access, or repeated read errors days or even weeks before the drive becomes fully inaccessible. The decisions made during that window often determine whether the data can be recovered and at what cost.
The first rule is to stop writing to the affected drive. Every write carries a risk of overwriting data that has been marked as deleted or relocated by the drive's internal remapping. Ordinary system activity, indexing services, and automatic updates continue to write in the background, which is why simply leaving the drive connected and running is not safe.
The second rule is to avoid running repair utilities at the file system level. Tools such as chkdsk or fsck will attempt to repair the structure of a file system that may be failing because the drive beneath it is physically deteriorating. A successful repair in that situation can make recovery significantly harder by relocating and rewriting metadata on failing sectors.
The correct first step is to disconnect the drive and, if the data has any business value, arrange for a sector-level image to be taken on professional equipment. Imaging is non-destructive, produces a working copy that can be analysed safely, and preserves the original state of the drive in case a second attempt is needed.
Acting quickly, but acting correctly, makes the difference. In our own case records, drives brought in within the first 48 hours of symptoms appearing have a recovery rate roughly double that of drives that continued in use for a week or more.
