isolate-try booting with minimal hardware connected, like psu+mobo+procie+1stick memory-if d mu boot, try replacement method,meaning ilis ilisi ang parts with known working one. but usually kani imo blema na mu ON lang ang mga LED but no display(assuming working ang monitor) ang usual suspect ani is memory or powersupply. if wala sa duha motherboard na
try also to reset bios or replace the battery.