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My computer suddenly stopped booting up. I just came back from a week long trip, and it was working fine before I left. When I power up the computer now, it seems to power up just fine (leds on, fans working), but then there's no output on the screen at all, and there's a noise that seems to be coming from the HD, like it is trying to read something. After the noise starts, it does 6 cycles and then stops. I'm not sure but I don't think it did this noise when the pc was still working. I tried using the onboard video card instead but it made no difference. What could be wrong with my computer?

EDIT: Here's some information on my desktop

Motherboard: Asus M4A785-M
Processor: AMD Phenom X4 955 black edition
RAM: 2 2GB kingston
HD: 1TB sata (dont know the manufacturer)
VGA: ATI 5770 1GB
PSU: 650W cooler master

I've got both Linux Slackware and Windows 7 on it. I bought it october 2010, its pretty new.

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Desktop or Notebook?, Make and Model, Which Operating System? Edit your original post to include this information. – Moab Feb 5 '11 at 17:12

Your hard drive has potentially crashed; remove the hard drive and attempt to at least boot into the BIOS. If that fails your motherboard is most likely to blame.

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If there is no output to screen at all then the PC probably hasn't got as far as the POST – Tog Feb 5 '11 at 16:09
I did that, and didn't change a thing except for the HD noises. I guess the problem might be in the motherboard then. Its so weird though, nobody touched my computer ever since i last used it, about a week ago. – David McDavidson Feb 5 '11 at 23:40
@bullettime It could be an issue with the PSU however the fact that it does boot up leads me to believe it is an issue with the motherboard – Aaron McIver Feb 6 '11 at 1:24

It could be a few things - firstly (I know this sounds stupid) make sure all cables are plugged in. If they were, next... unplug everything other than power, keyboard and screen

From what you have said, I would assume the error is either with the Power Unit, Motherboard or graphics card.

(I have read Aaron's answer - possible hard drive, but unlikely. It sounds like it is powering up then going to safe/standby. Your machine should boot, just come up with an error if it was the hard drive.)

(Only if you have a beeper/speaker) We can quickly see if the motherboard is dead - Try to unplug the memory - start up and if you hear a beep code (no memory) then the motherboard should be good. If you do not hear anything, the board may be dead, but you can try a few other things.

If you don't have a beeper/speaker, start here:

If the motherboard has internal graphics, I would next try plugging directly in there or using a different graphics card as we need to diagnose if the problem is with that.

If you do not have any way to test the graphics and have an internal beeper/speaker, you can try just unplugging it all together - if it is able to proceed with boot (e.g. one beep), it means that the problem was with the graphics.... however you have to remember if the board beeps on boot, and also, not every machine boots without some sort of graphics output.

(left in the above to help others, I have seen your motherboard does have internal graphics).

If there is no speaker, or alternate graphics card to test, it is hard to proceed.

However, if you get an image through the internal graphics, then the problem was with the graphics card.

If you do not get an image, the problem is either either the power unit or motherboard.

I would try unplugging everything other than PSU to motherboard. This includes optical and hard drives.

If you are able to boot, the power unit is not outputting enough power to all devices and you need a new (possibly more powerful one).

If you are not able to boot, most likely (in my experience) the motherboard has gone, however you still can not rule out a faulty PSU.

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... Just be careful, may also want to read something I just wrote in my blog, from a job a couple of days ago... – William Hilsum Feb 6 '11 at 0:08
Unfortunately I dont have a beeper. I guess I should've asked for one when I bought my computer. When I try to turn it on, the power led and the fans works normally, shouldn't they not work if the problem was with the PSU? – David McDavidson Feb 6 '11 at 13:15
@Bullettime - not if it is just faulty - I will admit it is highly unlikely, (I would say most likely either the GPU or MB) but you can not rule it out completely. – William Hilsum Feb 7 '11 at 0:38

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