4 Pin Motherboard with 4+4 Pin PSU

If you check the two 4pin plugs, one of those will fit the 4pin Cpu socket, the other won't
once you plug that in you should be sorted, but it will not post until the Cpu has power
Moto

Yeah i know it fits but my concern is because one of the 4 pin connectors stays unused, so if that isn't a problem i don't know what could be the cause of the system not working.

The CPU receives all of its power through that 4-pin CPU Power connector so it must be connected to the power supply or it will never boot.

did you put back the 20 or 24 pins connector to the board

The four pin connector that isn't used doesn't matter for your board,
if you had an 8pin block then obviously you want to plug the whole thing in,
it would function with the one 4pin, but if you have eight you would use them,
you are fine with the four pin as you only have a fourpin socket
Moto

I unplugged everything and connected my old psu with all the other components, the sb_pwr light is on and green, but the system won't turn on, i seriously can't think of anything that may cause it.

Did you try bread-boarding before placing everything into the case?

Breadboarding: http://www.tomshardware.co.uk/forum/page-262730_13_0.ht...

I unplugged everything i plugged since i started to upgrade the pc yesterday, and tryed with both the old and the new psu, it's the same pc i was using before, i just changed the gpu, the ram, and the psu, i think it has something to do with case's cables and their positioning in the mobo, my mobo is too old and too dirt for me to check if the 2 pins have names around it, but i think it doesn't, i also read that the powersw doesn't has an obligatory position, the leds and all that sort of wires aren't essential for the motherboard to power on aren't they

Try breadboarding...it's a great troubleshooting tool in your situation.