Thank you guys, many people have answered me so far and I really appreciate it.
The only sign of life come from the led near the ethernet port (the orange one).
No sign of life come from the Hard disk, so I tried with the one that I'm currentely using for my laptop, and even the ethernet led doesn't light on.
Then I tried with an exernal usb HD, it spin up and the ethernet led light on, but still won't power up.
It's really a pain in the ass.