Yesterday we moved someone's computer parts into a new case and the bastard didn't start when we finished. Everyone had a grounding strap and the mat was also grounded. We took everything out and checked if it might have been a part. We tried other power supplies. Other cables for the power.
In the end, we nearly wasted 2 hours and I finally took a good hard look at the motherboard's instructional manual. After a fourth time of looking at the front panel jumper settings I noticed the power switch wasn't connected correctly!!!
The damn thing was on "Green Switch" when it was supposed to be on "Soft Power Connector". Basically, it's in human nature to make this mistake, because what does the eye jump towards first when your trying to connect the computer's switch to the motherboard? "Switch"! Holy crap this has got to be the biggest load of crap.