Hi, I have a AMD Athlon 64 X2 Dual Core Processor 5200 processor, with a original AMD fan and heatsink. The pc randomly cuts out with heavy CPU use so I did mem test and ram is fine, I also fully cleaned the 4 fans on the case, I cleaned the heatsink and cpu fan, regreased the CPU with the correct compound so the pc is as good as new. Still getting cutoffs. I have been watching the CPU temp rise with Aida and I reckon its shutting off at around 70c. The CPU fan is spinning at 3000rpm. I have set it in the bios so its on contant 3000 rpm speed.
It has to be a CPU issue as the pc only cuts out when the CPU gets hot, I cant understand why suddeny the CPU is overheating if the fan is spinning ok, its been fine for 2 years. I have also replaced power supply with a spare one I had?

Any tips please