OK, so my MBP 5,1 has been a rock solid machine save for a flaky optical drive, but it had been getting extremely hot, especially while gaming. I mean >90 C hot. So today I opened it up to be greeted by a colossal amount of dust and fuzz. Took it outside and thoroughly blew it out; then removed some enormous dust bunnies from each fan housing with a toothpick. Now it's much cooler; I can game all day and never peak above 80 C even on the 9600m GT graphics. So, if you've had your MBP a while and it's running hot, blowing the dust out might do the trick!