Wipe it free: secure wiping software
When it comes retiring PCs at the office or at home, regardless of whether their final destination is a tip or to be sold to recover an investment, it goes without saying that a computer's drives need to be wiped. For the corporate environment, you're going to want to make sure no sensitive data is left behind however benign, and for the home you don't want leave any trace of personal details or credit card transactions that could be picked up and used in identify theft.
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Story added 6. April 2012, content source with full text you can find at link above.