Makes me remember an experiment done long ago (w95). Upgraded a (good working) HD to a larger one. Then did a test with the old one (no real use for it), had a very powerful magnet (from a large speaker) and did my best to try to destroy\erase the HD content. Put it back in the pc for testing, worked fine, booted like before and all files were still intact, no sign of damage whatsoever. Made me relax regarding HDs and normal external magnetism sources.