No make, model, age, story but what you gave.
Sadly it means your PC needs repair. As details are so slim I can't offer much other than ask for more and for you to reveal how many PCs you've fixed and if you know what a CMOS battery is without a google.
When i try to start my PC, only the LED light up when i press the power button, but nothing inside seems to be working, and nothing shows on screen. All the cables are pluged in, this just came out of nowhere, i would really appreciate i you could help me, thanks

Chowhound
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GameFAQs
GameSpot
Giant Bomb
TechRepublic