Just the light is off I can hear the fans inside the computer.

I have been having difficulties starting my computer. Every time I push the power button the computer turns on but doesn't fully boot. The monitor stays off, there's no power light on the power button, and Im unable to turn it off with the power button, I have to use the main power switch in the back. I was wondering if anyone has any ideas about what is going on. Any help would be greatly appreciated