hard disk activity on XP

Windows XP Home on Fujitsu Amilo D laptop newly bought.
The hard disk is noisy on this machine and is almost
constantly active. I have disabled services such as
monitoring and so forth, and the indexing service. I can't
disable event logging. Every couple of seconds the hard
disk light comes on and it goes click-click click-click,
then waits for two seconds and does it again. It is
driving me up the pole. What is causing this activity when
the machine is doing nothing (nothing useful that is), and
how can I stop it?