How about this?
If you look closely at that first one, that slug went right through the hard drive... seperating the drive platters
Seriously, flatlander said it. If you are giving the computer away and want to "wipe" it of data, the safest way is to format the drive. Then use a partition utility to erase the partition, recreate it, format it again and then install a fresh OS. This will keep all but folks like the NSA from reading what was on the drive before.