I have a core duo macbook 1.8ghz and for a while now it has been getting very very hot. So that if im watching a video and looking at a web page the macbook will turn off. I have checked to see if there is anything grabbing all the cpu and there isn't. I have also tried to reset the SMC but that didn't help either Since i have brought it I have changed the harddrive from 80gb to 120gb, and the case has been changed due to cracks. I know macbooks tend to run hot, especially the older ones. But it never used to sound this loud or shut itself down. Any ideas? Or is it just getting on.