Kernel_task_(0) Eating Up Processor Cycles ?



i am experienceing weird performance dropouts so i went into the process viewer and found a kernel_task which is eating up anywhere from 2% to 46% when the powerbook is just sitting there doing nothing (all apps closed). The %CPU varies.

It says in the properties that the process group ID is wheel (0).
I did a search in google and came up with an apple tech doc stating that the wheel group has been replaced by the admin group since 10.3 ... i am running 10.3.9.
I found quite a lot of posts about people complaining but no real answer to what this process is and if it's a buggy extension or sth else that can be cured.
This is very annoying, especially for audio work in Cubase SX3 with virtual instruments where how you can hear how this impacts performance. The more apps i have open or things i'm doin at the same time, the bigger the %CPU of the kernel_task

Is there any way to find out more about this mysterious thing and is there a way to calm it down or switch it off when needed. Or is this just normal housekeeping i shouldn't or couldn't worry about ... the performance dropouts shure
seem real