If you are really concerned about your data and want to delete it forever, then you may try any of the below methods :-
1) Physical Destruction - Also, suggested by shesagordie. Just used a sledgehammer and smash powerfully on your hard drive. BANG.
Please note - Two drawbacks of this technique which I want to share with all
i) Creates lots of environmental waste. You are contributing on increasing the heeps of E-waste.
ii) Hard Drive can't be reused again.
2) Data Erasure Software - My personal favorite technique of permanent data erasing. The software works on the principle of overwriting with many passes. One such software which I often use is Bitraser, as it is secured and certified.
3) Degaussing - This method magnetically erases data from magnetic storage media. Always remember, degaussed hard drive can't be reused.
All best solutions are shared with poster, kindly acknowledge. Thanks!!!
Apologise for delay in replying....
Thanks for the solution David, but could you please confirm, whether my Windows OS is affected due to this process?
Software driven approach of data eraser by above mentioned software, is independent of OS system. So it don't affect your Windows OS.