Unfortunately, within 30 seconds of the heads being loaded a high-pitched whining noise began to be emitted from the drive, implying a potential head-to-disk contact was taking place. The drive was then powered down and the disk pack and heads were carefully examined. Thorough examination revealed that Head #4 on the drive (which reads the bottom surface of the lowest data platter) had 'crashed' into the disk surface and scraped away a concentric ring of oxide material, permanently damaging the platter. This is a good time to point out the advantages of not experimenting with your primary source material when performing digital archeology experiments!

Src: http://www.archive.org/details/2011-cdc-disk-archaeology-fen...