Start up problem

Hi, i have recently bought a new pc due to my last two computers both suffering from the same problem.
I push the start up button, both green and red light immediately turn on and constantly stay on, fans all run, disk drive seems to operate fine (etc open close), hard drive is running but the computer does not beep like it usually would the screen stays blank and it will idle for hours in this state.
If there is a fix that any body knows about it would be greatly appreciated

Thank you in advance