S.M.A.R.T. is your friend
Yesterday I heard a frightening noise out of my PC. You know that sound when the hard disk reinitializes in the middle of the day, making a sound somewhat like "squeeeak-smack" (sorry, don't know how to describe it better)? As this is normally not a sound a healthy disk should ever make, I was immediately very tense.
Only then I realised that when I had installed my system the last time I forgot to install Panterasoft's HDD Health freeware. It is a tool that monitors your hard drives vital signs through the S.M.A.R.T. (Self-Monitoring Analysis and Reporting Technology; see Wikipedia for more details) interface incorporated in (almost) all modern drives.
I have always been wondering why there is no such thing in Windows out of the box, as it certainly is no very new standard and it is really a good thing to know in advance, when a hard drive is going to fail. Anyway, when I installed and started HDD Health it immediately told me about a disk temperature exceeding the critical limit on my Samsung hard drive. It was at 58°C, the recommended maximum specified by Samsung for my SP1614C (specifications here) being 55°C.
I don't know how long it has been exceeding the limit, but I sure ask myself why I mounted my hard drives into neighboring drive slots when I had another one free. So I re-mounted the lower disk to leave a 3.5" slot free between the two drives. Since then, the temperature has not risen above 38°C. I just hope, it did not take any permanent damage. Sure as hell I'll remember having the S.M.A.R.T. monitoring tool running from now on!