hardware conflict...
Basically it generally boils down to graphics card, RAM, motherboard or CPU...
Remove the graphics card and try powering the computer...obviously it won't boot but the thing to check for is if your computer beeps at you....if it beeps at you then try reseating the graphics card making 100% sure that it's correctly in the slot and try powering up...if it doesn't beep then you need to do the same thing with the RAM...remove it and see if it beeps at you...if it does then trying reseating the RAM.
If it doesn't beep after you've resat either component, but it beeped when the component wasn't in the slot, then chances are that component is faulty.
If it still doesn't beep it's the mobo or CPU...in which you'd need a seperate computer to try that out..
You can make sure your motherboard isn't grounded, but taking it out of the case, laying it on something like cardboard and powering up the system, making sure you're close to the case so you can plug in the PC speaker to listen for beeps.
If still nothing then you are left in the dark as to whether it's CPU or mobo...and if you don't have another comp, be it your own or a friends, then the only thing you can do is RMA both