Peoples' private information needs to stay private, even after it has been erased. Wait a minute, after it's been erased?
Have you ever given away an old computer or diskette, deleting the files off it, or giving it a quick format to make sure your information is gone? That might not be enough to stop some one from easily recovering the information!
When you delete a file, normally the operating system and file system say, "ok the file is gone!" but at the physical level the information is still there. If you were to run a recovery program you would be able to see information that you have deleted.
In order to get rid of old data you actually need to write over that same physical location on the hard drive several times to make sure it is gone, or at least much harder to recover. The standard for most government agencies is to do a seven pass wipe. That means that the hard drive will be written over with various sequences and random data seven time to be considered clean.
There are many end user applications that can assist you by wiping data as you delete it multiple times, however it will slow down your system significantly if you are deleting large amounts of data. For the average home user I wouldn't suggest wiping your deleted items more than three or four times, unless you are really worried about the information being recovered.
If you plan on wiping away the entire computer there is some applications that you can use that run from a boot diskette that will allow you to wipe the entire hard drive from start to finish. This process takes several hours, usually left as an "all nighter." (One of those programs you start before you go to sleep!)
You may be thinking, this is great for writeable media, but what about one-write media, such as CD's, DVD's and things like that? Stores sell pretty cool CD shredders, or machines that will indent the media with little holes or pock marks that make it unreadable. But my personal favorite (Do not do this, it's probably dangerous, and will be bad for the unit) is to put CD/DVD media in the microwave for two seconds. It makes the media in to this really cool spider web sort of cracked design that I like to hang on my pin board. As I mentioned, you shouldn't do this method, it's probably really bad for the microwave and might send some bad wave lengths through the room in to your brain, and it will make your microwave smell bad. You have been warned.
The final problem you might have is with hard drives that have failed, often they die at a random time, with whatever information you had on it. You don't just want to throw it in the trash, just in case someone gets creative and tries to recover the information. I highly suggest that you either disassemble it nicely with torques screw drivers (most of them use torques), and trash the plates inside, or be create in how to smash the entire drive until it's broken and flat. If you do decide to dissect it gracefully, the magnets inside are super strong and are great for hanging calendars and heavier items from metal cabinets.
Data security and privacy is such an important topic, always treat your media appropriately as to reduce your risk of passing on private information mistakenly!
Ken Dennis
http://KenDennis-RSS.homeip.net