[robespierre]

If you really wanted to degauss a deskside computer, in theory you could use a handheld degaussing wand. They are designed to remove magnetization from magnetic tape recorders and drives, to avoid corrupting tapes played back or recorded on those drives. So their purpose is opposite to large degaussing tables: it's for data preservation rather than data destruction. I have no idea what effect such a wand would have on a hard disk drive, but it would obviously be hazardous to the data and also the servo patterns.