Hi, My PC has been working fine recently until about three days ago - it won't power on. The motherboard (ASUS P4S533 with a Pentium 4 1.8Ghz 400Mhz CPU, 512 + 256 PC2100 DDR Memory) has the green LED which means there's certainly power getting to the motherboard. I've even reset the CMOS, whipped out the battery, put them back and still nothing. I also unplugged all my internal devices and pulled out all external devices - still nothing. I even resorted to purchasing a QTEC 550W PSU rather than the 300W that came with the case - still nothing. Is my motherboard dead ? Could it be the switch to the motherboard ? Having a look at the CPU, it doesn't seem to have any burn marks on it.

It could be shorting out on the case. If you still have the box that the motehrboard came with get it and unhook the ATX connector from teh board. Place the board on the box. Plug the ATX connector into the board then the P4 12V connector to where it goes. Keep the CPU in with the heatsink and fan on, also just have one stick of RAM and the video card in place. Remove all other expansion cards. Turn the PSU on by it's switch, take a flat head screw driver and breifly short out the two pins where the power button usually connects to. This will act as a power button whilst the board is out of the case. If still nothing happens check all the jumpers on the board especially the clear CMOS one making sure it's in teh run position. Remember to pull the 512 stick of RAM out while testing, that could be your problem here. If none of that works remove the RAM and the CPU and trying powering on with just a fan connected to the CPU fan header -- nothing else. If nothing happens, and the PSU is definately working, something has gone wrong with the board. The CPU fan should spin if the board is good, as when the two power pins are shorted the power goes to the board -- to the CPU fan.

Thanks for your help ben. looks like the motherboard has died for some reason. ah well, i'll have to get a replacement.