I also worked in computer repair. I once a long long time ago bought a presario and had it for about 2 days. *Hint* If she owns one of these things I am truly sorry. I am with everyone else here - what it sounds like is a definate thermal issue. theres one other thing you can try after you clean it out - and this sounds FUNNY but its a proven working method. run it, and if it crashes let it cool then place it on top of a huge boxfan on high. the air will help cool it enough to experiment. if it still crashes after this, then your issue is not as likely to be a thermal one, as most of the heat in a laptop is dissapated thru the bottom. (thats where the mobo is)
I used to do this with a PC in the summer that I overclocked. The internal case temp would get too high on real hot days, so I slid the side off and bungied a fan to it. is it pretty? no. Quiet? no. effective? You bet.