So, when I rubbed the magnet over both sides of the disk I was effectively erasing the data by writing 1s all over the disk? Would building an electromagnet be a way to get a negative field to wipe the disk to all 0s? I really would like to get these demagnetized, if possible, but I'm not really magnet-saavy. I understand I need to get the magnetic field on the disk to 0 gauss. That's all.