When the computer won't turn on, but still LED light lit on the motherboard, here are the potential causes. If there is beeping sound while starting the system, reference the motherboard manual; those beeps will indicate the problem.
RAM
Improperly seated RAM will cause the system to not turn on. This is because RAM is integral to the computer's operation. Turn off the system and unplug the power cord, then re-seat your RAM modules.
