I have the exact same problem!
i bought the DV2500 laptop in october of 2008 for my wife as she "liked its looks"
being more practical, I bought a Lenovo thinkpad for myself (which runs absolutely flawlessly)
the Hp DV2500 has always had issues, it would sometimes turn itself off with no warning, and as a result, files would usually end up corrupted, the amount of times vista was reinstalled because of corrupt files due to this laptop shutting off, was ridiculous, not to mention the amount of personal files and work that was lost!
in the past 3 months (when the machine is now out of warranty) the machine has experienced more severe problems, namely the laptop will display not 6 screens but a very scrambled pattern of multiple coloured pixels on the screen, it is just very garbled and unreadable. when the machine is turned off and on again, the HP splash screen is not shown, instead a blank screen is shown... i can see the hard drive light ticking away as if its loading windows... again, within a few minutes, the laptop turns itself off again.
i must mention here, that like almost every other post here, this laptop runs EXTREMELY hot! i am not talking the kind of hot that will make you move your hand after a few minutes because it gets uncomfortable, i am talking about so hot that you cannot even touch the palm rest as it is red hot! like the OP, i can smell the melting of the internal components and plastics!
like Rayzer has written very extensively in his posts above, this laptop has a very poor design. the vent at the back blows only mildly warm air, so the majority of the heat generated is being circulated inside the machine, causing the heating issue. the vista sticker on the underside is now unreadable as it has practically burnt black, one of the underside panels has actually warped with the heat and is now slightly bowed.
the processor is a T7300 C2D and the usual NV8 GPU with the thermal pad which is worse than useless.
Rayzer also pointed out above that he used a self made fan and placed it a the back of the vent in the laptop and this somewhat stablised the laptop.
unknowingly, whilst 'enjoying' a fault free day with the laptop the other day, only for it to fail the very next day, i investigated what could have been different.. i discovered that my wife had a tabletop fan on her desk behind the laptop which was keeping her cool... and it must have been dissapating a lot of the air inside the laptop via the rear vent also, which helped keep the laptop "trouble free" for that day.
hardly a full time solution to an item designed for portability!
i used to work for HP offering technical support and they were supposed to give us 3 weeks training on the items we would be supporting... we were on the phones just 24 hours after we were hired! my previous I.T. skills got me up to standard, but my colleagues who joined with me were left to educate themselves on the product that HP couldn't be bothered to educate them on... so customers were receiving very little in the way of support.
the bottom line is, with so many issues surrounding the DV series of laptops and possibly other models, HP should be made to acknowledge that, yes, this is a design issue, and yes, it is their fault. No company is too big to ignore what is obviously a world wide problem (I'm in Australia), and HP's persistence to ignore this issue, will hopefully prove to be as serious a flaw as this red hot piece of melted crap that I paid a lot of money for!