Computer won't boot after changing cases

I bought some new components for my computer (fans, case, blu-ray player, hard drive, 2 more ram sticks) and it will no longer turn on since it has changed cases. I used standoff's. I unplugged all but the bare necessities, including the new RAM, but it still won't work. The motherboard has a green light, but there's no sign of life besides that (no fans, no psu light, etc). I also took the motherboard out of the new case.

When I press the on button, I can hear a small clicking noise. It only clicks once, and I have to deprive the psu of power if I want to replicate it by pressing the power button. I'm pretty much positive that the click comes from the power supply. I have a little psu tester gizmo, and my power supply seems to work just fine when I plug it into it; it lights up and everything, and the readings seem normal. At first I had thought that the click noise was coming from my CPU, so I took off the heatsink and examined it. I found that there was a small amount of thermal paste on the wrong side of the cpu! I'm not sure if it was a hazard or not, but I realize that if it caused pins to conduct with each other then my processor is probably dead. Also, I suspect that the thermal paste would have been there when it was still in my old case, when it was still working. Anyways, I cleaned it up, and nothing has changed. I don't understand why my psu would click if my cpu was the problem. Furthermore, I would still expect the case to come to life a little bit when I press the on button. Is my cpu dead? Does it sound like something shorted on my motherboard?

Any advice would be appreciated...
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  1. That my friend sounds a lot like a dead PSU. If it was the motherboard, it would probably just reboot often, or not go past the post. The complete lack of fans spinning or any signs of life points to the PSU first, motherboard second, and the CPU paste issues also is kinda looming in the distance.
  2. I had that problem before. It was because I had shorted out the mobo. Put one of the brass anchors in the wrong spot so it was shorting out the mobo from underneath. Removed it and the problem was fixed. Really dumb mistake, but fortunately it made no damage. Hope yours is a similiar situation.
  3. Work systematically through our standard checklist and troubleshooting thread:
    I mean work through, not just read over it. We spent a lot of time on this. It should find most of the problems.

    If that doesn't help, strip everything out of the case. Remove the standoffs. Lay the motherboard down on the motherboard tray and with a pencil, mark the location of the mounting holes. Place a standoff on every pencil mark.

    I have tested the following beep patterns on Gigabyte, eVGA, and ECS motherboards. Other BIOS' may be different, but they all use a single short beep for a successful POST.

    Breadboard - that will help isolate any kind of case problem you might have.

    Breadboard with just motherboard, CPU & HSF, case speaker, and PSU.

    Make sure you plug the CPU power cable in. The system will not boot without it.

    I always breadboard a new build. It takes only a few minutes, and you know you are putting good parts in the case once you are finished.

    You can turn on the PC by momentarily shorting the two pins that the case power switch goes to. You should hear a series of long, single beeps indicating memory problems. Silence indicates a problem with (in most likely order) the PSU, motherboard, or CPU. Remember, at this time, you do not have a graphics card installed so the load on your PSU will be reduced.

    If no beeps:
    Running fans and drives and motherboard LED's do not necessarily indicate a good PSU. In the absence of a single short beep, they also do not indicate that the system is booting.

    At this point, you can sort of check the PSU. Try to borrow a known good PSU of around 550 - 600 watts. That will power just about any system with a single GPU. If you cannot do that, use a DMM to measure the voltages. Measure between the colored wires and either chassis ground or the black wires. Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire: 5 volts always on. Tolerances are +/- 5% except for the -12 volts which is +/- 10%.

    The gray wire is really important. It should go from 0 to +5 volts when you turn the PSU on with the case switch. CPU needs this signal to boot.

    You can turn on the PSU by completely disconnecting the PSU and using a paperclip or jumper wire to short the green wire to one of the neighboring black wires.

    A way that might be easier is to use the main power plug. Working from the back of the plug where the wires come out, use a bare paperclip to short between the green wire and one of the neighboring black wires. That will do the same thing with an installed PSU. It is also an easy way to bypass a questionable case power switch.

    This checks the PSU under no load conditions, so it is not completely reliable. But if it can not pass this, it is dead. Then repeat the checks with the PSU plugged into the computer to put a load on the PSU.

    If the system beeps:
    If it looks like the PSU is good, install a memory stick. Boot. Beep pattern should change to one long and several short beeps indicating a missing graphics card.

    Silence, long single beeps, or series of short beeps indicate a problem with the memory. If you get short beeps verify that the memory is in the appropriate motherboard slots.

    Insert the video card and connect any necessary PCIe power connectors. Boot. At this point, the system should POST successfully (a single short beep). Notice that you do not need keyboard, mouse, monitor, or drives to successfully POST.
    At this point, if the system doesn't work, it's either the video card or an inadequate PSU. Or rarely - the motherboard's PCIe interface.

    Now start connecting the rest of the devices starting with the monitor, then keyboard and mouse, then the rest of the devices, testing after each step. It's possible that you can pass the POST with a defective video card. The POST routines can only check the video interface. It cannot check the internal parts of the video card.
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