Thanks for your reply. It's a SATA one, and started to trouble out of nothing. No strange noise, nothing at all. One thing I noticed and forgot to mention is that when it happens, HDD is recognized as a 67Gb one, when it's really a 1Tb disk.
Anyway, I'll give a try to you tip, and try an external case, just to check if anything can be done.
My mobo (a Gigabyte DA-G31M-S2L) is being a pain lately. Maybe it's time for an upgrade...