Having worked for one drive manufacturer doing failure analysis on hard drives, I know of a fault canned "stiction". This is when the lubricant on the platter gets sticky, and the heads stick, preventing rotation. It happens most often on older, low hours drives, and is recognised by a repeated, rising tone. This is an attempt by the drives bootstrap code to shake it loose. Very often things can be freed up by rotating the drive with a flick, so that the platter tries not to turn, while the case does. If a flick by hand doesn't work, and as a last resort, tap the corner of the drive with progressively harder implements, so that it rotates.