How to erase/wipe hard drive safelly securelly by overwriting data?

What are fastest, yet secure ways?

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I used to burn Hirens boot CD http://www.hirensbootcd.org/burning/

and then selected "Boot menu" entry after computer start.
Then one can select many tools.



I selected Hard Disk Tools

and then WDClear
http://contents.driverguide.com/content.php?id=112186&path=Wdclear.txt
http://www.ufaa2.com/NewTechSite/Downloads/Files/wdclear/WDClear.ZIP
http://www.chip.de/downloads/WDClear_29716704.html

it writes clear and write zeros to drive and the process taken 45 minutes (150 GB HDD, 10,000 RPM)

The Hirens Boot CD also features second HDD secure erase software, "HDD Erase". https://en.wikipedia.org/wiki/HDDerase