Wiping hard drive TOTALLY

System

http://www.garner-products.com/HD-2.htm works for me although it does tend to fry the electronics as well

TBH I think some of the suggestions on here are totally OTT unless that you are worried about SIS looking at it. Most people, assuming that they even try to get something off it, will normally just try some of the free recovery tools around. If you have 'friends' that start using commercial/forensic methods then change your friends and just keep/trash the disk.

zaax

Drives are extremely cheap and as he is a computer wizard I bet he can get them even cheaper - so why would he want it.

Gyro

You could use the free 'Eraser' or something similar, to delete and overwrite any files on the disk, then as someone else suggested, use the free 'Recuva' to see the state of any deleted files left on the disk. You can also use Recuva to do another overwrite on those files if you want.

Alternatively, just tell him that someone has suggested you put the hard drive into a container, (like one of THESE), and use it as an external USB storage drive for your own computer, and so you're going to do that.
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