New case for old motherboard, POWER SW or general power problem

computer was a hp a300n. I needed a bigger case, a friend gave me an Asus case. I took my motherboard out, screwed it into the new one and connected the power supply. I put the fan into the motherboard, the 20 pin power into the motherboard, the cpu fan back into the motherboard. I then put in my graphics card (since have tried without it ). I connected the POWER SW, the RESET SW, the LEDs, and when I hit the switch on the front...nothing happens.
No juice.
I notice not even a light turns on on the motherboard, or a fan spins. I have tried a different known working power supply unit, nothing still. At one point I had heard a small click when I plugged in the power cord, but nothing now. Please help I need this computer running ASAP.

computer specs; hp pavilion a300n motherboard model ASUS A7N8X-LA
1gb ram, radeon x800 pro agp, no hard drives or optical connected because nothing happens anyway!! help!
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More about case motherboard power general power problem
  1. Wait, I didn't see any mention of you connecting the case switch to your motherboard... you did that right?
  2. I presume you turned on the power switch on the BACK of the PSU, too. Does your system have a 4- or 8-pin power connector for the CPU (usually located on the mobo close to the CPU) in addition to the main 20-pin power input connector? If it does, system will do nothing without that connection.

    If it's not one of those things, re-examine VERY carefully how you arranged the standoffs for mounting the mobo in the case. On a new build or relocation job like yours, one of the common mistakes is to put a standoff in the wrong place and cause a short circuit under the mobo, which "kills" the PSU because it shuts down to protect itself and the mobo. There should be a standoff mounted in the case ONLY under mobo holes used for screwing the mobo to the standoff, and NONE anywhere else. While you're at it, look for a loose screw under the mobo, just in case.
  3. Same scenerio here. Just traded my cases on an upgrade and nothing. I have power to the fans and to peripherals, including the case. I thought my AGP card went bad but nothing even trying a back-up card on a PCI slot. The power supply is fairly new(board is 3 year old ECS K8m-800).

    I went ahead and ordered a new board and CPU upgrade.
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