MBP boot issues, GPU very hot, crashes soon after turning it on

Question

Hi!
I just got a call from my Dad about his MacBook Pro (older Core Duo model, not Core 2 Duo). That's why I couldn't yet check the problem out first-hand and the information is a little vague - sorry about that. It's running the newest version of Snow Leopard 10.6.8 and is generally up to date.
The issue: He turned the MBP on after being away and not using it for one week. He said it didn't boot properly and crashed a few times before even starting up. And the fan was very loud. He managed to boot into the User Interface once, and he said that the average system temperature in the status bar (Temperature Monitor from Bresink software) didn't show the usual ~60°C but was higher, and when he clicked on it to see the details, the temperature of the GPU was way up, around 90°C. CPU temperatures were rather normal, on the other hand.
He could hear a fan spinning, but I guess it's still possible that just the GPU fan died?
Or is there only one fan in the whole system and the problem must be somewhere else?
What could he do to find out more about where the problem lies?
Thanks a lot!
If necessary, I will drive the few hours and go check on his MBP personally, so if needed you can also post some advanced steps that a typical dad couldn't perform.

Answer 1

Thanks!
I called him and told him the steps to do the SMC reset, and apparently that seemed to do the trick.
The MBP is now running normally and with cool temperatures again! (so far)
I asked him some more details about how it behaved earlier: Apparently, the computer completely shut itself down after a short while. The temperatures it displayed for the GPU ranged from 96°C to 104°C!
Funny how that one chip can screw up the whole system. But I wonder what causes those SMC screwups?
I remembered now, that I had to do the SMC reset a few times already in the past years on his MBP. None of the previous screwups were as severe as this one (so that the computer wouldn't run at all anymore). But they have been quite numerous, considering other MBPs of friends never had to do an SMC reset once.
What could be wrong with that particular MBP and SMC chip?
Anyway, thanks again!