Could be the dreaded nVidia chip problem, especially if you have the 8600M series graphics chip, problem meant to be fixed for the 9X00M series. Google your graphics card number + heat problem.
Is the BIOS up to date, as it dictates fan action mainly.
My DV2000 failed 3 times so I got money back, under Euro law as goods not fit for function as described - they had the machine more than I did, so obviously not fit goods. Finland only tolerate 2 failures I think.
Mine was fulltime on a cold metal pad with 2 fans and still failed 3 times with 2 new motherboards and GFX chips.
The smaller the laptop and bigger the GFX and CPU the more troublesome heat is to control in the confined space - spray air to keep out dust, cooler pad, ensure BIOS up to date is all you can do.
My end solution was buy the Vaio AW - 18 ", SSD drive for OS plus 500 gb spin disc and 9400 GFX, runs cool so far.
Sony just gave huge price hike €2400 to €3700 for it though.
You could also try undervolting the CPU with RMClock some laptop gurus swear by it to reduce laptop CPU action - thus heat to on demand and run cooler and at a lower voltage.
Mikhail says Mia-ow to Zane, at the moment he is manipulating cattery staff back in Ireland while I am in SD, Ca. My first RB Petrov was ex RX drug trial cat at St Vinnies Hospital in Melb the Vet Faculty stopped all cat drug tests in Australia, cats have next to zilch oxidation of most drugs (acetominophen/paracetamol kills), they use sulphonation so extrapolation of results to humans was useless. Their anaesthetic dose of xylazine is half that of a cow ! Cats are not dogs, they are women in fur coats ! Petrov loved catching snakes for my mother, presents on doorstep, hehe.