Inspiron 560MT won't power up

Hello,

I have an Inspiron 560MT since last february, working very good until now.

Yetserday I left my computer for a while, so it turned into sleeping mode by itself.

When I came back, impossible to turn it on again, so I pushed the power button for a few seconds to put it off, and since this time it won't power up anymore. I have an orange steady light on the power button, fans are all working full power, no power for mouse and keyboard, no signal on the screen......

I tried to put it off and on again several times, cleaned the inside (which was quite dusty), but nothing to do, it won't power up.

I am thinking of the graphic card or the motherboard, maybe burned, but I am really bad at computers, I don't even now how to recognize or to find them into the computer. Also I am just using it for work matters, so that would be unexpected. However a new game has been installed on this computer very recently, of course compatible with the system, so I don't see any problem coming from it (also it was working very good).

Please I need help, all my work is on this computer, I didn't had time to back up yet !!!!!!

Hope to have quick answers !!!