I've got an Athlon 1800XP system (with Antec case and 400 watt PS) I built last spring that has been working fine until two days ago when the system just shut down in the middle of surfing the net. The odd thing is that when I try to restart it, I see the power light on the case briefly flash on and then off but nothing else happens -- no fans or anything. I'm guessing its a fault in the power switch on my case or a power supply problem. Another option is a MOBO issue. Can anyone help me narrow this down based on a similar experience. To test any of these possibilities may require me to go out and get a second case and PS or another MOBO, so if anyone feels they have a better guess than I do, it might save me money or at least the hassle of multiple put together/tear down cycles.
Is it a generic PSU? How much dust buildup is inside the case. Did you have a power surge recently? Do you have a Volt Meter that you could test the power with. Many local computer shops will let you test out a PSU. I know they do here in Kansas City. You can either buy the PSU and if it doesn't work take it back for a refund. I'd make sure they allow you to do this first though.
Just another thought. Make sure that it isn't shorting out on anything. Remove the motherboard from the case and place on a static mat or something else non conductive. Then pull out all non essential components and see if It powers up. Also unplug all your hdd and cd roms. It's a lot of hit and miss but you'll eventually figure it out.
Thanks for the suggestions. It is an Antec PS and is only about 4 Mos old, so that shouldn't be the problem (unless it's defective). The case isn't too dusty. On that thought, however, I vacuumed out the case and around the power switch and PS. No change. I'll try to remove everything that is not necessary and try it again.