Here is the pin configuration of an ATX power supply, in case you need to make any "homemade" changes to it, such as aux power for other devices. (NOTE: THIS IS FOR ATX12V ONLY! OLDER POWER SUPPLIES HAVE SLIGHT CHANGES THAT COULD CAUSE CRITICAL DAMAGE IF NOT HANDLED PROPERLY!)

1 - ORANGE: +3.3v
2 - ORANGE: +3.3v
3 - BLACK: Ground
4 - RED: +5v
5 - BLACK: Ground
6 - RED: +5v
7 - BLACK: Ground
8 - WHITE: Power Good
9 - PURPLE: +5v Standby
10 - YELLOW: +12v
11 - YELLOW: +12v (OMIT for 20 pin ATX connector)
12 - ORANGE: +3.3v (OMIT for 20 pin ATX connector)
13 - BROWN: +3.3v Sense
14 - BLUE: -12v
15 - BLACK: Ground
16 - GREEN: Power On
17 - BLACK: Ground
18 - BLACK: Ground
19 - BLACK: Ground
20 - WHITE: -5v (Used only by legacy ISA add-on cards. May be removed.)
21 - RED: +5v
22 - RED: +5v
23 - RED: +5v (OMIT for 20 pin ATX connector)
24 - BLACK: Ground (OMIT for 20 pin ATX connector)