guys I don't know if any of you ever had the issue, or have heard of it: as far as I know, this problem only happens on laptops, and when the system is idle. That's a power management issue, most likely originated in the bios somewhere. the hard disk heads are being re-parked again and again. That's really upsetting and this is supposed to save energy. Hard disks have a limited (to about 600.000 IRRC) number of load cycles, and the issue is ridiculously making their life cycle shorter.
I first had the issue in Linux (clicks every ten seconds). There are may threads about it in Linux forums and I found that adding the line "hdparm -B 254 /dev/sda" in a file called rc.local (located @ /etc/rc.d/rc.local) would solve the problem, at least as long as the laptop is AC powered.
I had this same issue, but to a much lesser degree in Windows, so I didn't mind. But things have changed for some reasons, and now the clicks happen more and more often in Windows, and I don't like it. The thing is that the OS should override the BIOS to regulate this behavior, and even Windows doesn't seem to that very well. I even tried o switch from AHCI to IDE (before a reinstall of the OS) and nothing changed. So AHCI doesn't seem to be the culprit. But the issue does come from the BIOS: the clicks happen while I'm in it. Hard disk is not damaged, first it's almost new, and second, like I said, I don't have clicks anymore in Linux since I modified that file.
Now, I found a Win32 version of the Linux "hdparm" program, but it seems to require that UAC would be permanently deactivated to work. Even when granted admin rights, hdparm for Windows doesn't have any effect as long as UAC is on...I think; and anyway that's a program for Linux and I for one am surprised that Windows alone can't manage that.
I found tens of threads from people complaining about the same issue, always on laptops, also MAC laptops, others with Dell laptops. It seems to concern only systems with AHCI enabled sata controllers. Any comment or help on this would be appreciated ;)
ps: I have an ACER 5735Z laptop (bios updated to the latest)
edit: just an example of what can be found:
edit: I should have added, any change in the power management settings (hard disk section) in Win7 has no impact on that. Also, forgot to say hard disk activity light is flashing very regularly when the system is idle.