Hard disks are sensitive things. Spinning metal disks with magnetic read/write heads hovering micrometers above them. Many folks dont take enough care of their Hard Drives, and only find out that they have been damaged too late, when data has been lost.
If any of you are wondering how hard you have to knock a Hard Drive to affect it – watch the following clip, where you will learn that even shouting loudly can have an effect. So take care when using HDs near any kind of vibration, no matter whether it be from drilling into a nearby wall, or even just shouting at the drive.