it's a TVS diode. removing it may get the drive working again. it's there to protect the drive from overvoltage. it's like a zener, but has a much higher current capability. if it's shorted, it's probably why the drive is not working. i have repaired a few hard drives by replacing blown TVS diodes, and about 70% of the time, that's all that was wrong with the drive. remove it, and see if the drive works. if it works get as much data as you can moved off of it and once you have the data off of it, put the drive aside and don't use it until you get a new TVS diode for it.