I have a computer with z75 motherboard and i5-3570k CPU. It has been running fine for the last 2.5 years, when I built it. No overclocking applied to the computer.
Suddenly today, computer shuts off in the middle of use, and then won't boot. Opened it up and the motherboard LED indicates postcode 'C', which indicates a problem with the CPU. I'm confident all the wiring etc. are correct since it was working fine.
 
 
I suspect that it could be the CPU fan/heatsink or the CPU or the motherboard. How would you suggest I go about narrowing down the culprit? Also some questions:
1. When I turn on the computer, only fan that starts spinning is the one on the power supply. The case fans and the cpu fans do not spin. Is that normal function when there's a post code 'c' or could it be a problem with the fans?
2. Would a faulty CPU fan/heatsink cause such problem when the CPU is fine? (ie. post code C, computer not booting up). 
 
I'm currently thinking of maybe buying a new cpu fan/heatsink, and try installing it, and see if that solves the problem. If that doesn't work, maybe i'll buy a new CPU and try it out? And if that solves the problem, return the new CPU to the store I bought from and request a RMA from intel since the CPU seems to be the culprit. If that doesn't work, well, I guess the problem's with the motherboard? Or can anybody suggest other possible causes?
Also suggestions for better procedure than what i'm planning to do are very welcome. Thanks in advance.