Trip
Sorry, but I suck at explaining stuff :P
The first thing you should do is disconnect everything from the motherboard except the power supply and the power on switch. Make sure you remove the RAM, any add on cards, usb devices, keyboard and your mouse.The less stuff that's connected, the easier it will be to track down the problem.
Check that the back of the board isn't shorting out on anything.
Check that your CPU is fitted correctly and the processors fan's plugged into the right pins on the board.
If it still wont power on and you have a spare power supply, then try the other one with the board.
You can try resetting the bios etc. if you like, but I don't really think it will do much good if the boards not even starting.
EDIT: Sorry I didn't see your last post about the fan.
Check your manual for the pinout of the fan. It should still let you connect it to just 3 of the pins. Red wire to + and black wire to -.
Check that the back of the board isn't shorting out on anything.
Check that your CPU is fitted correctly and the processors fan's plugged into the right pins on the board.
If it still wont power on and you have a spare power supply, then try the other one with the board.
You can try resetting the bios etc. if you like, but I don't really think it will do much good if the boards not even starting.
EDIT: Sorry I didn't see your last post about the fan.
Check your manual for the pinout of the fan. It should still let you connect it to just 3 of the pins. Red wire to + and black wire to -.