To have your laptop completely dead/not turning on (or only having a momentary flash of LED lights and some fan spin) can be a serious problem. Most commonly it is the motherboard which is a very expensive component to replace ($500 ~ $1000+ depending on make and model, etc). It is also common that a laptop that presents as dead can be revived if the fault is:

• flat battery and/or faulty AC charger
• stuck in hibernation or some "twilight zone" state
• faulty ram or hard drive
• a repairable motherboard issue.