For as much as people worry about the information collected by companies and the government, they often discard incredible amounts of personal information when they upgrade to a new computer.
Individuals aren't the only ones guilty of handing out information on old computers; in their annual study of second hand hard drives British researchers found a trove of information about a top secret U.S. missile defense system and other corporate information.
The research group also found payroll information, social security numbers, banking information, corporate secrets and even pictures of patient wounds at a nursing home on hard drives purchased from several countries on eBay and other auctions.
Of the hard drives examined, 34% contained some information that was of personal nature to some person or company. Even though stories like this illustrate the dangers of not erasing old hard drives, most people don't understand the amount of information stored on their old computers or how to remove it.
While you could destroy your old computers like Lockheed Martin currently does, there are better options than drilling holes in your hard drive. Both Windows and Mac operating systems will allow users to format a hard drive, but if you really want to make sure that everything is gone you should look into a low level hard drive formatting tool like DBAN.
DBAN is a simple to use file erasing tool that overwrites each piece of data on your hard drive leaving the previous information unreadable. DBAN can be run from a floppy or CD on your old computer so you don't even have to open the case. There are several other options for erasing data covered in this PC World video.
Just like you would shred your credit card statements before throwing them out, you absolutely need to wipe your hard drive before you throw it away, sell it or donate it to anyone. Thanks to the above programs anyone can wipe the hard drive without paying a professional.
Seriously, if you can burn a music CD and turn your computer on you have the smarts required to clean up your data. If you don't feel comfortable going the DIY route you can ask your neighborhood geek or take your computer in to the shop, but for most users this isn't needed.
If you don't plan to wipe your hard drive before disposing of it you may as well tape a copy of your social security card, drivers license and birth certificate to it to speed up the process.
US missile defense plans turn up on eBay'd hard drive