Ok, so a friend's laptop gets very hot, very quickly, then just cuts out dead, the fan seems to be working and it's never under any sort of excessive load. Frankly, I'm a bit stumped. I'm pretty sure that it's the CPU, but I'm not sure why. I was thinking open it up, clean the insides and re-seat the heat-sink with new thermal compound. I have a week until I next have a chance to look at it but some ideas would be helpful in case this is stupid/doesn't work. Also, while I'm here, the same laptop drops the connection to two different wireless routers, frequently and at random intervals. I'm going to be performing a re-format and fresh windows 7 install with the newest drivers of course and failing that I have a spare wi-fi card to replace the old one with. Is there anything I've missed with regards to this, bearing in mind that I've ruled out both routers as potential causes.
You have a buildup of lint and fibers in the fan heat exchanger. Disassemble the laptop and clean, or hope for the best and use pressure air through the heatsink vent. The heatpipe/radiator looking bit is clogged likea dryer with lint. If this is an HP DV series, odds are it has a dried out thermal pad on the the gpu and needs a copper shim and new compound (found on ebay)
I thought that might be the problem, it is indeed an HP. Just looked up copper shims, surprised I'd never heard of them, I'll have to ask my friend the exact model Also thank you!
In my personal experience, wifi drops are the death throes of an HP DV series with a Geforce 8000 series graphics chipset. Like ASSEMbler said, check the vents/heatsink for accumulated dust, hair, etc. If it does have a Geforce 8000 series card, your friend may want to get one of those laptop cooler jobbies to extend the life a tad (I wouldn't normally recommend these otherwise). I couldn't even begin to tell you how many HP warranty information sheets I printed out for people with HP DV6000s. Best of luck to you.
You can send it to someone for $75 and get it reballed with lead. Worth the money, and while you're at it add the max speed cpu within reason like a T9200 or whatever.
Sorry for taking so long to reply, I didn't get to go and visit her until today I bought a shim, installed it, used new thermal paste for everything and cleaned the masses of dust out of the heat exchanger. All seems well and no need for a re-balling. Interestingly, the CPU was the best possible for the motherboard despite the sticker on the casing saying 'centrino'. She has never paid for it to be upgraded and she bought it new which seems odd. And thank you for all the help