Could be a number of problems, but before listing all of them... what lead up to this? Is there a history of problems that lead up to no boot or it was all of a sudden?
Also what make/model computer or if custom build all specs please?
Most common are power supply problem, however if this is a new build and the CPU is unsupported or damaged etc or wrong RAM installed etc you can get same results. More info is needed about what lead up to this so that I dont type 10000 words on all the possibilities
