I had this same problem with my other computer and never found out what died.
Yesterday, I shut down the computer normally (construction people doing work in the front yard and they killed our last machine clicking the hydro on/off),so last night after they left I hit the power button and walked away.
Thinking it was booting normal....
Today nothing works? you can hear the fans running and the power light is blue and the HDD clicks 1-2 times and the machine just hmms.