I came into my room and noticed my pc was running much louder than usual so I opened OCCT and saw my cpu was running at 100% (nothing was open) so I opened every single stress test application to make sure they weren't running then I went to task manager and closed everything that was open. It's not going to overheat my CPU (AMD Phenom II 955 BE) because it is only running at 42 degrees and I have a big cooler in it (Hyper 212+) but what is the problem?
When you open your task manager, click on processes, then click on "CPU". Whatever is eating your processor will be on the top of the list and it should show you what percentage of the processor is being used.
What virus scan did you use? Not all virus scanners will catch all viruses.