I've had an i5 3570k processor for around 3 months now and I am starting to become quite worried with the temperatures. While running Prime95, the CPU temperature will reach around 50-55C whereas Core 0, 1, 2 and 3 will reach around 80-85C. I have an Arctic Cooling Freezer Xtreme Rev.2 CPU Cooler installed. I think that I might have installed it incorrectly because other people with this cooler can run this processor with the core temps only reaching around 60C at clocks of around 4.2 GHz. I am only running at a max of 3.8 GHz.
i5 3570K @ 3.8 GHz- Arctic Cooling Freezer Xtreme Rev.2 CPU Cooler
Asrock B75M Motherboard
8gb G-Skill RAM 1866 MHz
ATi Radeon HD 6870
500W Cooler Master PSU
If you think you didn't install it correctly, remove it, clean it & the processor of thermal paste, put fresh paste on the CPU, and then sit the heatsink onto the processor, following the instructions it comes with and make sure it's all the way down, with pressure on the CPU's heat spreader.