Hello, everyone! When using OS X I notice there is a regular clicking sound made by the hard disc. I met the same problem under linux, and it was easily fixed by the program "hdparm". However, When I tried the equivalent "hdapm"(http://mckinlay.net.nz/hdapm/) on OS X, it didn't work at all. Could someone tell me how can I solve the problem?
Any suggestion will be appreciate.

Try unchecking the "Put hard disks to sleep when possible" in Energy Saver in System Preferences

Thank you very much. But The problem is still there after unchecking that.
I tried "hdapm disk0 max" again, and the err code is:

disk0: WDC WD1200BEVS-75UST0
Setting APM level to 0xfe: FAILED: APM not supported

That's strange because my hard disc do spport APM and a similiar method works very well under UBUNTU linux.

Exactly the same problem here and also exactly the same HDD (WD 1200BEVS) ...

I had the same issue with a Samsung drive and was able to fix it by upgrading the firmware. Maybe there is something for your drive as well.

It is definitely a controller issue!
I've had three different HDD, both in capacity and manufacturer in my HP dv6716ez and they all did that. I even had a Genuine Apple HDD in it! my HP ran for more than 7 months, 24hrs a day and had no errors!

Now, my NEW Alu MacBook 2,4 is as quiet as a mouse!

SticMAC