The computer does nothing when I push the power, other than the LED inside the power button glows orange, and the fan on the CPU twitches for a moment. There is also an LED on the mobo that lights up when I plug the machin into the wall.

This to me seemed like a short. I looked everywhere for something shorting the board and nothing worked. I took the mounting apart and put it back together. I reset all of the brass mountings themselves making sure there was one for every hole on the mobo with no extra and making sure each mounting had a screw attached. None of this worked.

I looked at the CPU but found no scorch marks or anything else wrong with it. I re sat the RAM. Neither of these worked.

I also tried starting the machine with only the mobo and CPU fan connected to the power supply. This did not work either.

Does anyone have any ideas on something I'm missing? What else could this be?

Is this a new build?

Did this system ever work?

My next suspect would be the PSU itself. If it is a high end model most are fitted with self shut downs in the event of shorts.

Or the unit itself might be faulty. Did it ever work?

Yes, it worked fine. My wife opened it to air-dust it. Then it wouldnt turn back on. I figured she bumped something loose causing the short.