Computer has begun to power down on its own

For some reason my computer has begun to power down on its own when it gets caught up on internet explorer. I usually find myself going from page to page and it will take the page longer to load and all of a sudden it will power down as if I held down the power button. My computer is an HP Pavilion purchased in 2005-2006 it has XP Home Edition Version 2002 Service Pack 3 as the OS. AMD Turion 64 Mobile 512mb of RAM. I run McAfee VirusScan Enterprise Version 8.0. Any insight on why this may be occuring would help greatly and maybe get me on the track of fixing this issue. Thanks.

Reply 1 : Computer has begun to power down on its own

http://reviews.cnet.com/4520-11319_7-6240575-1.html

Reply 2 : Computer has begun to power down on its own

I regularly blow out the fan on my laptop with a compressed can of air. The last time i dis this was about two weeks ago. I also make sure that there are no obstruction between the surface and the fan intake where ever my computer lies.