Guys help,any advice to prevent this?

[steliosem06]

Last month I bought a WDC HDD 500gb and it run perfectly.I didnt really use it,but i was satisfied.Today,I decided to use it for some really,really big files to transfer,I first checked hdd sentinel and my hdd health was a solid 100%.So,while waiting for the transfer I went out for a while,and when i came back....HDD Sentinel said that my hdd was now at 6% health and that 65149 sectors had been lost!I had some reallt important files on it and now they are all lost. I know theres no way to fix this,but can you please tell me why this happened?

[northwind]

The drive was obviously degraded and you stressed it long enough to expose weaknesses (ie. weak heads and/or media damage) during the big files transfer.

We can take a look if you want, we are based both in Athens and Thessaloniki.
Till then, I strongly suggest you don't power up the drive again.