Sony Laptop freezing up, overheating?????

I have a sony laptop that is only a year and a half old. Its running windows XP home ed. Recently it has started to freeze up. The screen, the mouse, the keyboard, everything! Somebody said it might be my CPU overheating but i'm not too sure. It mostly happens when the fan is blowing out very hot air but has happened once or twice when the computer was relatively cool. There is nothing in the event viewer to tell me anything unusuall has happened. It has happened on occasions when there were little or no programs running. I have however noticed that when running AVI movies in particular the system is almost guaranteed to crash in a minute or so after startin the film. Does anyone out there have any ideas what could be happening?
Any help would be greatly appreciated.

Thanks

Ray

is there a second fan that has died inside? perhaps trying to download a utility to monitor fans, or use the bios temps and fan speeds if possible...

You should try checking the fans and make sure that there is nothing restricting it's airflow. Overtime dust might build up in where the air flows and that could stop the hot air from flowing out, thus, leading to overheating. If the fans on your laptop is dead you might want to refer to the guys over at Hardware Cooling and see if they have a replacement fan for your laptop. They were able to assist me in getting a replacement fan for my toshiba tecra 8000.