I have often experienced problems with disk drives that have been stored for a few years. They may work perfectly well when put into store but after sitting in a drawer for maybe 5 years they are kaput. And so I’m wondering if it could be due to the strong fields from the magnets either side of the voice coil—they are sitting just millimetres away from the platters. In normal use the orientation of the platter to the magnets is continually varying and so there’s no significant polarising effect but after a few years of standing motionless in this magnetic field I suspect the data fields on the platter could start to get polarised – effectively wiping the disk. Any physicists out there willing to comment?