Laptop dies after short period.

Looking for some help here. I have the Samsung RF510. Its quite old but it used to work absoutely fine. recently its started playing up and I’m getting random unexpected shutdowns.
I’ve cleaned the fan dusted etc, but it still does it.,
Bios settings I have reset to defaults, and I’ve checked the 8GB of ram that I’ve installed with memcheck and they are fine.
The error I was getting have changed a few times but the recent one was:
The speed of processor X in group X is being limited by system firware. The processor has been in this reduced performance state for 2 seconds since the last report.

after this I have changed power settings based on what I’ve found online to stop the cpu being limited to a percentage.
Ive opened it baesd on this video
https://www.youtube.com/watch?t=125&v=zTru8ktw_SU
Below is the motherboard with fan removed.
http://funkyimg.com/view/21CES
Could the placement of the thermal paste be causing this issue?
Any help or any advice would be really great!
Thanks all.
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Answer #1
What does windows event viewer say after it crashes? You should also check to see if your voltages are fine with hwmonitor
Answer #2
Check the temperatures under load too..
The thermal paste changed? May be a bit thick.
https://www.ifixit.com/Guide/Applying+Thermal+Paste/744