To ensure no data remains on your hard drive, data still remains for recovery despite deleting and formatting, use this software to overwrite data on the hard drive numerous times, the software can be found at http://hard-drive-eraser.en.softonic.com/?gclid=CJ...
Disk Wiping Standards
The government standard (DoD 5220.22-M), considered a medium security level, specifies three iterations to completely overwrite a hard drive six times. Each iteration makes two write-passes over the entire drive; the first pass inscribes ones (1) over the drive surface and the second inscribes zeros (0) onto the surface. After the third iteration, a government designated code of 246 is written across the drive, then it is verified by a final pass that uses a read-verify process.
If you have wiped you hard disk clean using the software mentioned, you would not be one among those whose data was retrieved by 2 MIT students as part of an experiment -
In 2003 two MIT students purchased 158 used disk drives from various locations and found more than 5,000 credit card numbers, medical reports, detailed personal and corporate financial information, and several gigabytes worth of personal e-mail and pornography on those drives.
Information as found on http://www.webopedia.com/DidYouKnow/computer_scien...