I am experiencing what appears to be the same issue. I have a Barracuda ES.2 ST3500320NS 500GB. During drive operation, while I'm loading information or a program, I hear the normal chatter a hard drive makes. But occasionally during that process I hear a distinctly metallic click, or even a slight crunch sounding noise. Its louder than the normal hard drive chatter sound you hear when the drive is reading data. Not only is it louder, its slightly higher in pitch.
In addition to this happening occasionally during hard drive operation, it ocurrs when the drive is idle. Now I know Windows tends to do things when a computer sits idle, but this is different. Every 5 or 10 minutes, even while the computer is sitting completely idle and Windows isn't accessing the drive, I hear the sound. Just a "cliiiick", or "crrruuunch" sound. It lasts for about 2 seconds. It doesn't repeat itself over and over in quick succession (not yet), but it happens constantly. Like I said every 5 or 10 minutes. I have alot of other computers in the house, and I swear, the only time I've ever heard noises of this nature was when I've had a hard drive eventually fail on me.
I'm concerned there seems to be no official word from Seagate about this particular noise. Is this just a quirk of their drives, and is normal to hear from them? Something we shouldn't be concerned about? Or are there plenty of their drives out there that don't do this, and it is in fact an abnormal thing to be hearing?
I'm sending the drive back to Newegg for a replacement, as it is within its 30 day warranty with them. I've only had the drive two weeks, and its done this since I first installed.