Over the summer I built a PC. Everything was going great until september, when my CPU (FX-4100) failed. I got a new one and that one failed and I did not get around to returning it until December. I just got the new CPU today and I put it in, and the CPU_LED red light came on, like it did with the last one. I have been through 3 CPU's since the summer and I am thinking it is either the motherboard (Sabertooth 990FX) or the PSU (Antec HCG 750) is the problem now. The PSU turns on and the whole computer starts up but it wont even POST. On the monitor, it says Unsuspported video signal. That happens when my PC doesn't POST. I know 200% its not the monitor cause i have the ps3 hooked up to it. The mobo may be the problem but how do I check to see if it is?
CPUs rarely fail. Check your Rail Volts with the PC powered on to eliminate PSU (Antec usually reliable) http://hardwarelogic.com/articles.php?id=5075
Otherwise try with a diferent GPU in case a fault on that is causing the problem.
Was your BIOS up-to-date?