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What Reasons Would A Computer Power Up But Not Boot?

My pc is was working fine yesterday and today when i try to turn it on, the CPU powers up, all the fans spins but there is no display, no beep sounds, no keyboard or mouse lights.

  • I removed and reseated the components.
  • Changed the RAM
  • There is no new hardware installed
  • Onboard VGA
  • Monitor works fine
  • changed the HDD
  • applied new thermal paste
  • removed the CMOS battery, drained the power and tried a fresh start

but sill im having "no display, no beep sounds, no keyboard or mouse lights"

can someone please tell me what the problem might be?

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How do you know the CPU powers up? Also, when it starts, do any of the other lights from the mobo connection flash? The HDD or power light for instance? –  camster342 Sep 19 '11 at 5:19
    
Any chance of trying it with a different/someone else's CPU? –  camster342 Sep 19 '11 at 5:21
    
@camster342, many people refer to the entire case as the CPU. I'm assuming LiveEn means the fans spin audibly so something's getting power. –  Hand-E-Food Sep 19 '11 at 5:54
    
the processor fan spins, hard drive spins, cd rom works. @camster342 there is no light in my MB –  LiveEn Sep 19 '11 at 6:01
    
@Hand-E-Food ah, that would make sense. Another clue to look for for the OP is to put your ear up to the HDD and listen for what sounds it makes. If it sounds like it's doing nothing, as in just a whine, or a regular whirrr-click, then the things most likely at fault are CPU or Motherboard. If it sounds like it has activity which sort of sounds like an irregular clicking or "zzzh" sound, then it might be the onboard VGA, which might still mean motherboard replacement, but might be able to get away with just putting a VGA card in. (sorry I know my descriptions of the sounds isn't very good...) –  camster342 Sep 19 '11 at 6:03
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marked as duplicate by Nifle, Mehper C. Palavuzlar, 8088, DragonLord, studiohack Sep 30 '11 at 2:43

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1 Answer

Top suspects for a no-beep POST failure (presuming your system normally beeps after successful POST) are:

  • Power Supply - It seems yours is probably fine, since the fans and HDD are spinning up. However, since it's the cheapest of these to test by swap-out, you may want to start here.

  • Motherboard - Next least-expensive to check. Sometimes a simple visual inspection will give it away, but you'll probably have to change it out to be sure.

  • CPU - Generally, the most expensive of these. Again, visual inspection of a clean CPU and the CPU socket might give away the problem. As with most parts, replacement is often the only real way to verify this suspect.

If you're unsure of whether or not your system should be beeping on a successful POST, (most do, but some don't) consult the manual for your motherboard.

If your system should beep on a successful POST, and isn't, my suggestion would be to first find or procure a spare PSU and swap that in. If that tests successfully, then you've found your problem. If the test fails, I would swap out the motherboard and CPU together.

If you prefer to homebrew your systems, now's a good time to just re-build the whole rig. If not, or you're short on budget, it's probably time to go to your favorite local computer retailer and pick up a new OEM system.

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