I put together a machine for a lady quite some time ago and she's had the same problem ever since it was setup. I've searched the net endlessly trying to find the solution (which almost never fails) but I can't find one that will fix this problem. Here it is: when she turns off her machine and comes back later to turn it back on, it doesn't do anything. The lights will blink, no sounds, the first time she pushes power but then nothing. I had her turn the power off on the PS and then turn the machine on. That was able to get it back on but once it turns on, more than likely it will turn itself off suddenly either during POST or boot up or once in Windows. Then the routine starts again. It seems dead, you reset the PS and then it might last a little longer, but then turn off, and so on. Sometimes this can go 4 or 5 times, with it lasting 10 minutes before turning off, but finally it will just decide to stay on and it will run great for as long as you keep it on, 3 weeks for example. But once it is shut down, it all starts again.

There's the problem, now here's the components and what I've checked/replaced trying to fix it. She has an ATX case, MSI KT4AV-L MoBo, Athlon XP 2100+, 256 PC3200 400Mhz RAM, 64MB GeForce 4 MX, CD-R drive, 40GB HDD, 17" LCD screen. It had a 300W PS at first, but I thought that to be the problem so I put in a 450W, didn't fix it. I called MSI and got a replacement MoBo, didn't fix it. I've swapped out the RAM, even trying some 266 Mhz chips, same problem. I've checked if any of the parts are overheating, I don't think they are since the machine can stay on for long periods of time, it just has troubling getting in the groove. The case has good ventilation and she has a UPS so the power coming in should be fine (I've checked that many times too). I don't think it's software related, we've updated every driver we can think of.

Diagnosis: I'm out of ideas and need help! She's very frustrated and I can't blame her.

Thanks,
Aaron

Try changing your motherboard, it could be an error in your BIOS (basic imput output settings)

On modern motherboards, the BIOS often has settings for sensors on the motherboard tracking temperature and voltage and stuff. They are able to display warnings or shut the system down when things go outside of the parameters that it regards as being safe to operate under.

I wonder whether you are able to disable these so that it never tries to shut down under "dangerous" conditions?