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What Reasons Would A Computer Power Up But Not Boot?

When I power on my computer it will not boot. It will not even go into bios or anything. It is as if it is not powering on at all, however the decorative casing lights turn on and the PC is making noise (like from the fans).

I am reluctant to think it is the power supply since some part are getting power. I do not know what it is though?

For the couple days leading up to this, the computer would make a loud noise and the screen would stop displaying anything. I had to reboot to get it to work again. Now nothing happens when I boot, except the case lights come on and it sounds like some fans are coming on.

Any ideas?

update

I disconnected a media reader, It then booted up and ran for about 5 minutes before completely loosing power instantly. I booted again and it starts to boot but instantly powers off before finishing booting.

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Does the motherboard beep at any time? Beeping codes reveal a certain hardware failure (depending on the motherboard version, of course). –  slhck Jan 22 '11 at 17:23
    
@slhck there is no beep. thanks. –  JD Isaacks Jan 22 '11 at 17:27
    
DO you have any self added on pci cards? Sometimes when those fail it prevents the whole system from running. –  a sandwhich Jan 22 '11 at 18:12
    
@a sandwich, I added the video card myself when I bought the pc a couple years ago, the media reader was recently just having problems though but its not pci. But I can try removing that. –  JD Isaacks Jan 22 '11 at 19:46
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Power supplies supply different voltages on different rails and some have more than 1 12v rail, so it could still be a PSU that is not working 100% –  Moab Jan 22 '11 at 23:06
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marked as duplicate by BloodPhilia, ChrisF, Nifle, studiohack Feb 3 '11 at 17:59

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2 Answers

This error is in my experience almost always the PSU gone bad. My very first step in error searching would be to test with another unit.

Another classic algorithm is to disconnect everything not crucial for boot and see if it makes any difference, but try another PSU first, it will probably save you time.

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I had to replace a CMOS battery the other day. They are about two bucks and can usually be found at CVS, Walmart, auto parts, etc. Especially if it is getting older, this may save you some hair pulling. I also had to replace a cable modem power cord yesterday which had been driving me nuts for about a week.

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I bought the computer around 2007-2008 would the battery be died already? –  JD Isaacks Feb 1 '11 at 16:42
    
It's not likely, but it's one thing to eliminate easily. I assume it is a desktop as you say "case lights come on". A laptop is a little tricker. I also support Daniel's procedure, but I'm brand new so I can't promote it. –  Bob Feb 1 '11 at 21:09
    
@John, just curious if you found a resolution for this issue? –  Bob Mar 7 '11 at 15:24
    
No not yet, I have been so busy lately I have just been using a different computer and haven't touched that one. I did disconnect the media reader which caused it to actually load the OS but then it still powered down immediately afterwards. –  JD Isaacks Mar 7 '11 at 17:48
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