open it up take out the magnet and wipe it over the disk repeatedly
There is aprogram called Killdisk that will do the trick. You can get free use of the program. Just download and off you go. It will write zeros to everything on the disk and wipe it to mil spec.
Repartitioning the drive makes it rather difficult to extract data, and rather quickly too. You can get a free tool from http://partitionlogic.org.uk/L
1. Find and take the hard drive out of the computer.
2. Lay the hard drive on the ground (preferably outside) and take a sledge hammer to it.
3. Take all the tiny pieces and bury them deep in the ground.
4. Ta-dah! One hard drive wiped completly.
Writing zeros to the drive will be more than fine, and you don't have to destroy the drive. If you're paranoid, do a few passes of random data. Anything beyond that is just insanity.Grab a Linux live CD. I keep a GParted live CD around for things like this. Open up a terminal and type the following.dd if=/dev/zero of=/dev/hdaThe /dev/hda needs to point to your hard drive. Make sure this is the only drive in the system, so you don't accidentally write over the wrong drive. It also might be something like hdb or sda. If you start the GParted software, it can tell you which device it is.Writing it over with zeros will take a little while, just let it run. You won't see anything happening on the screen, but if you see your hard drive flashing and hear your drive "crunching," just let it go until it's done.
badblocks -fw /dev/sda
enough for most uses