My problem is the same as many others I have seen listed. PC was working fine all these years, suddenly went to turn it on and loud fan noise, blank screen, pc won't boot. Have tried all fixes listed. Power cord is fine, f10 will not start BIOS. Took off back, cleaned fans, redid thermal paste on CPU/heat sink. No sign of overheating, capacitors all look good, am assuming it is motherboard or hard drive?? How do I check those?