Is there any way of finding out what is accessing the disk? Not only it shortens battery life, it is annoying while working in a quiet room.
When I had problems with irritating disk noises on a laptop it turned out that the problem wasn't so much disk access as an over-aggressive power management setting.
hdparm -I /dev/hda | grep 'power management'
should tell you the current setting. The default value seems to be 128, but what exactly that means depends on your hard disk. I found that changing the setting to 200 was a big improvement:
hdparm -B 200 /dev/hda
You can make the change permanent by editing /etc/sysconfig/harddisks.
Ron