Noise from Caviar Blue

I have a noise problem with a new WD5000AAKB PATA Hard Drive that i have just purchased.
The problem is that the drive is constantly making a clunking noise when it is idle.
I first noticed the noise some hours after the drive had been povered on the first time.
The clunking noise occurs with an interval between a few seconds and a minute and only when the drive sits idle.
This is the second unit that exhibits this irritating noise. The first one i got had the same noise problem, but only worse and I therefore had it replaced.
The noise is very annoying and i find it unacceptable and unbearable to listen to.
I have newer before heard such a noise coming from a hard drive.
I have run a WinDlg quick test and it came out ok.
How come it is making this noise and is my drive defective in some way?

I am running Windows XP SP3 and the drive is partitioned in two parts. C: with 25GB and a E: with the rest.

I have recorded two audio files to let you hear the clunk noise it is making.


I was able to find two WD articles regarding drive noise. See below: