A busy processor spiking to 100% utilization isn’t anything to be concerned about. Staying at 100% is something else entirely. This points to either a system that is being asked to do too much, a software glitch that is sending the processor into a loop or a virus.
Activities like video encoding, bit torrent, CD/DVD burning and gaming all take up processor time, and can in some circumstances send it to full utilization. This should happen rarely, and only when the machine is doing a lot of work. The utilization itself isn’t the real issue here. It may prevent you doing other things on the PC while it's working, but that’s more of an inconvenience that a problem. The main enemy of a maxed out processor is heat.
As the processor is supplied with voltage from a motherboard, it converts it into unstable energy to drive the processor. This conversion wastes some of that energy and radiates it in the form of heat. That’s why your PC gets warm, because the CPU, graphics card GPU, power supply and hard drives all use the same process. The harder these components work, the more heat they produce.
In order to combat the heat the CPU, GPU, and power supply unit (PSU) all have heat sinks and fans which help to keep the components cool enough to keep working. They have enough tolerance to cope with full use for a set period of time, but not permanently. Also as the components age, their effectiveness degrades, meaning their capacity to offload the heat from the source reduces.
So rather than spending money on aftermarket cooling, the first thing to do is to check out what is causing the processor to work so hard. For that we need the trusty Task Manager. So either press Ctrl-Alt-Delete or right click on the task bar and call it up. The Task Manager will show us what processes are running and exactly how much processor power they are using as a percentage of the whole. This is an ideal way of identifying greedy problem processes and finding out why your machine is running slowly.