I have a Dell Inspiron 560 - 5 years old. It is:
Dual Core i5 E5500@ 2.8ghz
6 Gig Ram
just put in Seasonic 620 PSU
room temp around 75 degrees
I see core temps up to 140F. I first thought the PSU would fix the issue, but it did not (another internal fan). This has been going on for several months (before Seasonic PSU). The CPU unit is kept clean. My thoughts now are thermal paste and a new core/heatsink fan?