PC doesnt turn on

I've recently built my own PC and after 4 months of it working fine its suddenly died on me, completely as I was watching a DVD! I press the power button and nothing happens...i have double checked the power cables, tried different PSU and even checked the button on the back of the PSU!

I have a P4 3.06Mhz
Asus P4S533-MX (Socket 478) Micro ATX Motherboard (MB-047-AS)
512MB DDR Ram

new PSU and fans have been installed since the crash.
I've tried different PSU, fans, CMOS battery
Have also removed from Case to see if something was shorting motherboard
and have tried to boot using a screwdriver over the power switch connector, still no luck.

Any ideas what it could be?

Since it's not the power supply (first thing to check), it's either the CPU or the motherboard. Most replace the motherboard first b/c it's usually cheaper, but I recently had the same problem with an AMD K6/2 500 on a FIC motherboard and it was the CPU. It wouldn't boot at all, but I could hear the hard drives spin up so it wasn't the power supply. When I replaced the CPU, it worked fine.

I think it is the CPU but i wasnt 100% sure!

Now i have checked everything apart from the CPU it has to be that!

Strange how it doesnt boot and beep at me if it was a dead CPU, as thats the usuall outcome of a bad CPU right? but in some cases it could just not boot at all? am i right in that suggestion??

I don't want to worry you, but you processor has blown once, is there a possibility of it blowing again. Do a quick check to see that there is nothing obvious. Fan not working. Thermal compound not applied correctly. Although both of these you would expect a thermal shutdown to have taken place. Check you BIOS to ensure this is set up OK. Check for foreign bodies like a screw floating around in your case. I don't suppose there was the chance of static damage around the time of your CPUs demise, did you have the lid off your case? Look around your motherboard for the smallest little piece of crap that could have caused a short. etc