No Boot. No Lights, Nothing

I have a Soyo K7VTA Pro in a Generic case. 900Mhz Athlon CPU 768Mb PC-133 RAM too many programs to remember printer scanner dsl connection. Running uneventfull since 14 months. I cvome home one day and it won’t start. No POST, no motors running, nolights, nothing. I would guess the power supply but I have no way of testing to get a satisfying answer. I have the skeletons of some old machines in the house but one has a different P/S connection that what’s on the Soyo P/S and the other one won’t start up no matter what P/S I use. The same can be said of the Soyo. What is the next step in troubleshoooting?