Kernel_Task Using Resources

I notice that according to Activity Monitor, Kernel_Task can start running a constant 18-25% CPU, 47 threads, 64 MB Real Memory and 764 of Virtual.

It continues to run at his rate despite what else I am doing on the machine. Just wondering what might be causing this. Most of the time it is at %0 CPU, but when I notice performance drops in WoW I check the Monitor and this is normally the cause.

Im running at 1.33 Ghz PB with 10.3.9, the problem has been around for at-least the previous 2 updates.

Thanks for any advice.

 

I have narrowed the problem down. It seems it only does this when I am connected to the internet via dial-up. Is this normal?