A high CPU usage reading typically indicates that your systems processor is running at full capacity while the current applications are running. Random shutdowns, sluggish and intermittent performance are common symptoms of high CPU usage. The CPUs task is to process the data which initiates and runs your programs.
I took it upon myself to write a guide on how to speed up your computer, targeted primarily at those individuals that would like to squeeze every last bit of life out of their systems. The reality is that, unless your system is very old, i.e. using very old architecture, outdated motherboard etc then there is very little reason why you should want to purchase a new one.