I have an old computer I built myself and it has worked fine for almost 4 years. Now it keeps on turning off without warning. It used to only happen when I tried to burn a dvd or watch a dvd. Over time it has gotten much worse. Now it takes me 10 - 20 tries to get the computer to stay on and then it won't even stay on for more than 12 hours. I have cleaned out the inside of the computer. I think it might be a power supply problem but the fact that it will work sometimes and stay on for a few hours leads me to believe other wise. I have checked for viruses, changed out and tried both of my 512 pieces of memory. All the fans seem to be working properly and it doesn't seem to be getting too hot but then again I don't know how to check the temperature of anything so that might be it. Please someone help!
one more thing I remembered was I bought a new samsung 19 inch monitor off my roommate a while back. The computer didn't really ever shut down until I used that. The dvd-rw problem made me believe it was the power supply but I just read another forum where someone mentioned their video card getting hot. I don't remember what kind of video card I bought but I do know that this problem didn't happen until this monitor was connected. I no longer have other monitors to try troubleshooting but this doesn't seem like a problem that would cause my computer to keep shutting down. thanks.
Keeps turning off, cleaning the dust out is a good start to help keep thing's cool... think I'd be tempted to try a power supply, if you can try a known good one at least it's one item thats been eliminated...
... although not a thinker like the CPU the power unit does more work than the CPU, it has to supply all the power on demand, even the heat that the CPU gives off, so guess this is a good place to start, it's the first thing that I would cast evil eyes on.
All you need for the bios to boot and be able to access the bios set up screen is just the CPU, RAM and Graphic card.. the rest can be disconnected even the ol' hard drive. So you can deduce it's just gotta be one of these things... ok, ok I didn't include the mobo and power supply ..
...supposing with just the bare essentials and all was working ok, you'd get a message something like 'Please insert the disc with the operating system on' or 'No hard drive found' it'd let you know one way or the other.
What happens when you press the power button is... the bios does a Power On Self Test (POST) if all is ok it'll give a bleep as it boots (and you'll be able to get into bios set up if desired) it then hands control over to the CPU, then the hard drive kicks up and loads data into RAM... and way you go.
So, we're looking at Power unit, Graphic card, mobo and CPU, I doubt the RAM would create a no go situation, sometimes removing the Video card and refitting it helps....
..same with the CPU but this is the very last option, when you remove this you need to clean and apply new heat sink paste, somewhere there is a post where refitting the CPU cleared such a fault cant say which section but was quite a while back.
There is always risk of CPU or even mobo damage when removing the CPU... hence, the very last option.
so the more times I try the worse it gets. I can no longer get windows to stay on at all. The best I get is the welcome noise when windows opens up and then it crashes. I can tell you though, when I originally thought it was the power supply and/ or the new dvd/rw I unplugged the power supply to the dvd/rw thinking it would allow more power for the rest of the computer and it wouldn't even start up this way. It would attempt to start like a car does with a dead battery. I even remembered to change the other cd/rw drive back to master and completely unplugged all the cables to the dvd/rw. So for whatever reason when this was unplugged the computer completely does not work. I just took out my videocard and put it back in making sure everything was clean and still get the same problem. I think the computer has officially kicked the bucket.
It's not as much as unplugging the DC feeds to the drive's, the power unit uses what you call 'switch mode' the RAW mains voltage is rectified then smoothed by a capacitor and then switched off and on at about 22,000 times per second.. or 22KHz per second, now then a failing supply can give all the correct voltages... but what about if the capacitors have deteriorated and allows this HF 22KHz ripple on the DC supply line whether the volatgae falls or not.
If you can get it to boot at all check the temperature and voltages in the bios set up screen, they are usually given a clue might be had here.
Always check by substitution or replacement no matter the device, this way we are not guessing and we can then say 'yep we've eliminated that.
The first goal is to get it booting in 'bare bones' mode... I can't recall saying but it's always better to disconnect all USB devices with boot problems.
HELP! my computer keeps shutting down. 
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Linear Mode
