Auto start computer

That wiki article is downright WRONG. If you short the power switch wires, the machine will just shut off in four seconds, just like what would happen if you held in the power button.
Check your BIOS. There may be (probably is) a wake up timer in there; you can set it for your PC to come on at a certain time. If you need it to shut off when designated tasks have completed, use the SHUTDOWN command at the end of your batch job or script.