Alot of proceses arnt CPU intensive so it wont use alot, I've got 41 process and 99 System Idle, woppde doo. My PC isnt even that awsome, it depends what the services are etc that are running. Im usually running firefox, msn and winamp which use probaboyl about 100mb memory max and are hardly CPU intensive programs. Running a game will cause alot more CPU usage.
So moral of the story, not all processes are CPU intensive so you wont get alot of CPU power.
Also did you know that your superdooper AMD 4000+ or whatever your running isnt actually running at the speed it says of say 2.2ghz. AMD cpus (modern ones) run at 800mhz when just browsing net etc to save power, intels only drop to 2ghz or something so it might use more cpu power at a lower mhz and show up are more CPU intensive than it really is.