Nice try ernyoka1, but that doesn't explain why defragging the machine fixed it as well or why the problem would switch to a different application later. Sarakat, before you spend money on a new fan and start pulling apart your laptop, try scandisk and see if it fixes any errors and defrag your machine. Then see if the problem goes away. If it does, it's almost definately hard disk related- if not, then it may be overheating.