I am assembling a custom PC. The configuration is below:

1. Motherboard: Supermicro X8SIL-F
2. Processor: Intel Xeon 3430
3. Power Supply: Enermax Modu82+ 625W.
4. Memory: Kingston KVR1333D3LQ8R9S/8GEC 8GBx1 installed in DimmA1
5. This power switch: Frozen CPU switch

When I turn on the PSU, the motherboard tries to start itself before I even push the power switch. The following happens:

1. The CPU fan rotates like once or twice, and then stops.
2. After 1-2 seconds, the CPU fan tries to rotate again and stops after about one or two rotations.
3. Finally, after another 1-2 seconds, it again starts and this time it rotates for about 3-4 seconds before stopping.

If I pull out the Power switch, and turn on the PSU, again the MB turns on itself and the following happens:

1. The CPU fan rotates like once or twice, and then stops.
2. After 1-2 seconds, the CPU fan tries to rotate again and stops after about one or two rotations.
3. Finally, after another 1-2 seconds, it again starts and the system boots properly

I am sure there is nothing wrong with any of the components, because I have two sets of identical components (2 MBs, 2 CPUs, 2 PSUs, 2 switches and so on). And both of the systems show the same symptoms.

Why is the MB booting up by itself? Why does it fail to boot when the Power Switch is installed? Is something wrong with the type of Power Switch I am using?

PS: the power switch is installed correctly, I have double checked the MB manual to make sure its connecting the right pins.