certain rails on the PSU could be dead meaning the computer could start up for a sec then shut down and what not, just because something is DOA doesn't mean it doesn't work at all, it's kind of like a car, just because the engine won't start, it doesn't mean the radio is dead.
Unfortunately if you don't have any spart parts laying around it will be pretty hard to troubleshoot your system, I really think you need to make sure that your PSU is working, even if you have to take it to a friends house and hook it up to their working PC to check it, once you rule that out, your next concern would be your motherboard. If your PSU works and your computer is not even posting a message on you monitor, more than likely it's your mobo
Unfortunately if you don't have any spart parts laying around it will be pretty hard to troubleshoot your system, I really think you need to make sure that your PSU is working, even if you have to take it to a friends house and hook it up to their working PC to check it, once you rule that out, your next concern would be your motherboard. If your PSU works and your computer is not even posting a message on you monitor, more than likely it's your mobo






