Hi all, i'm building a bar for my basement and wiring a car stereo into it. I'm using a power supply out of a old computer i had laying around, question is, i cant get 12v out of any power lines, i got 5v out of a purple wire and 3v out of a green wire, looking to get 12v out of the yellow wire but i cant get, i heard its switched through the motherboard, any ideas how to make this work???