It is the seller responsibility to pack item properly to ensure safe delivery.
You cannot "ensure" the safety of a HD shipped via general post, even with great effort and money spent on packaging. a 14 year old also probably knows that you're not going to get "safe secure" bomb-proof packaging from someone that charges 2euro shipment too. they might even know that it's more than risky shipping eggs (ie: an old rickety HD) through the post and not moan when they arrive broken and cracked, probably due to the postman's less than careful handeling.
anyway, i wish this guy good luck trying to get his 7eur back and hope he has learnt something from the experience!

let me just give an example: I recently purchased a Philips CM8833 mkII monitor from a guy on eBay. The listing showed the monitor in perfect working order. This for me settled that no matter what happened during transit, the monitor would leave the guy's home WORKING.
Now the only question i had to ask myself was: "am I prepared to risk the monitor being broken during transit?" I decided it was worth the risk, but if it HAD arrived with the tube shattered into a million pieces then I decided in my own mind from the beginning that I would not hassle the seller for a refund. Simply because it is the type of item which is inhernetly likely to break during transit, much like a harddrive (no matter HOW WELL you package it!).
I would NEVER have dreamed of giving the seller a negative or asking for a refund if the monitor arrived broken. Nevermind the "consumer legalities", it's a question of morals, and people being reasonable with eachother. One guy trying to sell his item and another wanting to buy but also appretiating that he is sharing the risk in some instances.
I took the risk to have that item shipped. It was my decision, I don't care about the power "consumer rights" grant me to _demand_ a refund. This is an individual amature seller, he's not insured like mega online stores such as Amazon, so I'm not going to make him pay for my lack of common sense.