i don't see anywhere that it says system idle process
CTRL-ALT-DEL, click on 'Processes,' Scroll down to the bottom of the screen - alternatively, actually, additionally, what processes are using the CPU?
You said that this has been happening "since you've had the computer" - is it new? If so, don't do any drastic self-help such that you void your warranty; call Dell and let them handle it.