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I'm running Windows 7 64bit and having some very strange errors. I have new RAM and a new Cooler Master PSU; I've ruled out the RAM already since it did the same thing with another new stick. I don't have a different PSU to test, sadly.

Now, when I installed Windows 7, there were some issues. I was installing to what was originally Drive F, which then became Drive C with the new install. Some boot files ended up on Drive D (Formerly C) and had to be copied over or I had weird boot errors. If there are any missing files that might cause what's happening, please let me know. But I ran SFC and it brought up no problems.

So, what happens is that when I'm just using the computer (blogging, photo editing, playing a game, doesn't seem to matter what I'm doing) it will shut down, as if the power just went out. I still hear things working in the case, either fans or the PSU, after the shutdown. When I press the power button on the front of my case, nothing happens. If I hold it down for 5+ seconds, nothing happens. I have to flip the power switch in back off and on, then press the front button. Sometimes my USB keyboard won't be recognized during boot and I have to unplug it and plug it back in.

The only error that seems to show up in event logs is a kernel-power one letting me know that the computer shut down unexpectedly, which I already knew.

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That new PSU would be my No 1 suspect. –  RedGrittyBrick Sep 20 '11 at 9:16
    
Could be the memory connection itself. Try pulling out one stick of RAM at a time from the memory banks and see if the symptoms continue after each is pulled. –  jmreicha Sep 20 '11 at 19:53
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2 Answers 2

I recently encountered a similar problem with a brand new Dell 8100. After days of trying to sort it I stumbled across an obscure post on a forum suggesting that I disable the hybrid sleep setting on my power plan. Done it and the machine has been stable since. I'd suggest you try that:

Control Panel > Type 'Power Options' > Choose "Change Plan Settings" for whichever plan you are currently using > Change Advanced Power Settings > Sleep > Allow Hybrid Sleep - set this to OFF.

Some machines will automatically vary the power plan so you may wish to disable to this on each of your machine power plans. Hope this helps!

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When this has happened to me and to family members, (and it's happened a few times) it's shut itself down due to overheating of the CPU. Improper use of thermal grease between the CPU and the CPU fan would be one guess; a misaligned CPU fan (where it's not securely fastened evenly to the CPU) would by my other. Either way, the fix is the same. Replace the thermal grease.

First, purchase fresh thermal grease (there are many brands, do a bit of research to find the kind you want or need.) Thermal grease is cheap, and a tiny tube will last a long time. It's cheap insurance.

Next, take the CPU fan off the CPU, and as you do, take note of how the fan is mounted and how the fan mounting hardware works. Also check to see if the fan is wobbly before you unscrew anything, that's a strong clue you're on the right track.

Look at the existing grease that is on the CPU and bottom of the fan's heat sink. If it's crusty and hard, or gobbed on any thicker than a sheet of tracing paper, that's also a strong clue that you're on the right track. The adhesive stick-on grease pads that fan makers used to use are horrible conductors of heat, and if you find one that might be the problem.

Clean off the exposed surface of the CPU chip and of the bottom of the fan's heat sink. I use dry paper towels to first mechanically remove as much old grease as possible, and then clean both surfaces with a paper towel lightly dampened with 70% isopropyl alcohol. Clean them to a bright finish, don't allow any old thermal paste to remain, and don't dump the liquid alcohol directly on the CPU. (If you still get the motherboard damp anyway, a blow dryer set to a cool setting for a few minutes will evaporate what's left. Be careful not to start a fire, alcohol is extremely flammable and many things on the motherboard will burn!)

Clean any dust and dirt from the heat sink fins and from the heat sink fan. Compressed air is good, a old toothbrush works, pipe cleaners, anything to get it clean.

The surface of the CPU is very flat silicon and won't need attention, but make sure nothing is sticking up above the top of it. The surface of the heat sink also needs to be flat, but because it's soft aluminum or copper it might be gouged or dinged through rough handling. Make sure it's undamaged. Be careful if you think you can use sandpaper or other abrasives to correct some damage, as it's very difficult to get the surface as flat as it needs to be without proper knowledge and tools.

(If the metal surface of the heat sink is damaged or the mounting connectors or hardware are damaged, strongly consider buying a new CPU cooler. Be sure to buy one rated to dissipate the amount of power your CPU draws - an 80W CPU chip needs a cooler rated to dissipate at least 80W.)

Apply a very thin and even coat of thermal grease to the CPU chip. There are really good online videos on how to properly apply thermal grease. A good coat is so thin as to be almost see-through.

Remount the heat sink and fan. When mounting the heat sink, be sure each of the four corners is equally tightened by the connectors. A stripped screw, broken plastic expander, damaged socket, bent piece of metal, anything like that can prevent even pressure from being equally applied to each of the corners. If the pressure is uneven, there will be less contact between the CPU and heat sink on that side, and that gap will cause the CPU to overheat. A proper mounting will feel solid.

Once it's back on, and secured so there is no wobble at all, be sure to reconnect the fan's power supply wire (they're often connected to a pin header marked CPU_FAN on the motherboard.)

Good luck!

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