My console wont turn on.

My Xbox 360 slim will not power up. When I press the power button the green dot in the middle turns on for about 2 seconds and then shuts off. I have checked all the USB ports and they are fine. I did notice the the light on my power supply stays green. Even when its not connected to the console. I took the system and power brick about and clean them of all the dust. It still does not work. I believe that there is supposed to be an orange light when the system is off. Could my system not be powering up because the light in the power brick is always green?