I have a new motherboard having a 24 pin power supply socket, but my power supply has a 20 pin plug. I tried the computer with it but it doesn't boot, and curiously the power light comes on without pressing the powerup button. Do I need to get a new power supply? Can anyone tell me what the extra pins are for? the help page on this site gives the molex pin arrangement, but the 20 or 24 plug pins are not given.