A Strange/Boring Problem of my New EIDE disk, call for help!

My new HDD is WD600VE. It repeats clicking(may be unacceptable) if I do not do read/write operations , but there is no such sounds if I copy files from one partition to another. Also I found that if I download files from internet with a slow speed(e.g. 50Kb/s) ,that repetive clicking occur.

I scaned the surface, no bad sector. I changed the other WD600VE, but the problem is the same.

My laptop is HP NC6000. Is it possible that the clicking is caused by low power supply? How can I identify the problems of my disk?

Thanks for any suggestions!

Maybe it's not the HDD that makes sounds ?
I have fujitsu s6210 and it's cooling fan makes quiet clicking on high load.