i've just bought a Maxtor drive that is very quiet. Diamond Max Plus 9.
I have four of those Maxtors, and a IBM 180GXP and Hitachi 7K250 in
the same PC.
The Hitachi is by far the quietest of those three types. I cannot hear
it at all. (not even when I remove the sidecover of my pc)
The IBM is normally very quiet too, but is well known for the
occasionally scary and loud noise
The maxtors don't make much noise in idle. My PC is very quiet so I
can hear some vibration, but in the vast majority of computers you
will never notice this, because of the noise from fans.
But the seek noise of the maxtors is quite loud. It's the typical
harddisk rattle.
It doesn't really bother me to hear when a disk is busy. I find the
idle noise much more important. But if you want your harddisk to be
quiet during seek also, you defintely do not want the maxtors.