Explorer.exe

Recently, my sister's laptop has been having some problems. Her computer has been running extremely slow (it takes 10 seconds to lead the interface for MyComputer). She said the computer began running slow about a month and half ago and just now decided to let me know. Well i noticed her CPU usage was flat lining at 100%. So, i went through some of the basics...ran an anti-adware program, ran nortan anti-virus and defragged her computer. Nothing. So i took a closer look at the task manager and saw Explorer.exe I know this is the graphic shell and the task menu and all that good stuff. But for some reason, it sits between 90-100% CPU usage. I also had noticed her fan was on the Low setting and with the 100% CPU usage over the past month, her computer has gotten extremely hot in numerous occassions. I am thinking the processor or some other part is damaged within the computer but before I have it looked at, i was wondering if anybody knew how to fix this in anyway. Any help is appreciated, thanks.

(sorry if this is in the wrong part of the forums)