How to turn off the HDD? How to reduce the overall noise?

[Constantine]

Hello,

My hard disc drive seems to be too noisy for me. I want to test, how 
much idle noise would the system make with the hard drive turned off. I 
do not want to unplug the wires, since I have had a lot of problems last 
time I did that. Is there any command / utility that can turn my HDD off 
for a minute or so?

Are there any other utility that may help me reduce the noise in my system?

Right now I have IBM Deskstar 60GXP 41.0GB IC35L040AVER07-0, and I am 
considering to change it to IBM (Hitachi) Deskstar 180GXP 60GB 
IC35L060AVV207-0, or may be even Hitachi Deskstar 7K250 80GB 
HDS722580VLAT20. Have anyone experienced any of those? Are they any 
different in the idle noise they produce?

My motherboard is AOpen AX4G-N Intel 845G(+ICH4) chipset.

Cheers,
Constantine.