How to Erase Data on a Hard Drive

Everyone needs to erase data on a hard drive at some point!

The File-by-File Method 
1. INDIVIDUAL FILES ELIMINATED, SOFTWARE REMAINS INTACT 

• To completely destroy a file, use a data-shredding program such as Digital File Shredder from StompSoft ($30). It takes a conventional "erase" a step further by actually writing over the file.  

The Whole-Drive Method 
2. ENTIRE DRIVE IS PERMANENTLY ERASED, BUT STILL USABLE 

• Completely reformatting your drive doesn't eliminate data.
• Many of the best data-erasing programs come from the same companies that produce data-recovery software. DataEraser ($30), from Ontrack, completely overwrites the drive.

The Power Tool Method 
3. DATA IS GONE, HARD DRIVE IS TOAST 

• Drilling four holes through the platters will ensure that they never spin properly again.
• Better yet, unscrew and remove the top lid of the drive, and go at the platters with a sander or angle grinder. Scuff the surface of the platters until all the shine is gone.

More here: http://www.popularmechanics.com/technology/how-to/computer-security/4212242