|Certain CPUs run hotter than others. For instance, it's not unusual for the P4 Prescott to run at the temps you mentioned.|
You didn't list which CPU you have or anything about your cooling setup, so it's difficult to offer any solid solution. While the advice given by probfixer may help with your overheating issue, if you in fact have one, but it will not help the 100% usage issue.
The usage problem is *probably* caused by a program, possibly an infection (virus, trojan, spyware, malware, etc), that is sucking the life out of your system.
Have you checked Task Manager & identified what is hogging the CPU?