If its internal HDD's that you plan to buy, avoid buying online as usually packaging is not good, the exception being prime. Even if you plan to take the HDD from prime to your house, they will bubble wrap it to protect it. This is one of the best things about prime. Ditto for online ordering. prime packs their stuff really well.
if its an external HDD that you plan to buy, do a recharge of 500 and above on freecharge.in, use a maestro card for 2x coupons. select letsbuy 500 off coupon and use one of these coupons and buy from letsbuy.com. else you will get a 500GB with already available coupons for 2.3k approx online. for more info look in hot deals section.