DPC Process & CPU Throttling

Hello Folks!

I have examined the DPC process using the program called process explorer by
sysinternals. When the computer is idle the CPU usuage spikes every so often
at a max of 2% usuage for the CPU.

As soon as I plug in the cable modem and connected to the internet the CPU
usuage and DPC goes erratic. The Deffered Procedue Call is using the process
at %4.69 and spikes up to %10 every so often. Also Hardware interupts are
constantly using around %3 - %7 of CPU usuage.

My questions are:
1) How can I find out whats the driver thats gobbling up the DPC usuage ?

2) Is it normal for the Hardware Interupts to be constantly using CPU usuage
and how do I find the Hardware Interupt that is also contributing to the CPU
usuage?

Thanks