|Okay, I'm sorry to see you are having that problem.|
Good attempt with the new PSU, but it would help if you said what was actually running at that temperature.
For some CPU's, 65 degrees celcius is an automatic shutdown temperature, this feature is on my motherboard and will likely be on yours as we have a similar BIOS. You can either disable this 'feature' (which I wouldn't recommend) and continue to fry your CPU until it dies or there's a safety hazzard, or you can check/replace the CPU fan and/or remove any dust.
If you chose to replace the fan (it'll be cheap and easy) then you'd probably be best to keep an eye on the temperature's of your PC. I'm guessing your nephew unknowingly used an old CPU fan.
You can get CPU fans for AMD machines from a few different places. Personally, your best bet, is to get a hold of an old AMD machine and take it's CPU fan. Of course, the only problem with that, is that the fan will have an unknown life span. A new one will cost around £1-3.
...It is simply phsychological analysis consisting mostly of theories I myself have to decypher and deter their respective plausibility...