I don't know what would be causing this. I did Ad aware, spybot, HJT, and AVG, and stinger. All were clean. Checked all my running processes and they were fine. Usually it is less than 10%. there is nothing big using it. right now it is at 100% while i am typing this. My CPU is an AMD 64 3000+. It just started doing this today. I did install a new HDD if that matters at all. I had to take it out though because it didn't work.