I need some help

Good day. I have got a pc with a Epox Ep 3VCM+ motherboard and 128mb 133 SDRam. The problem is the pc does not start. When I press the button to start up the computer, the power comes on, but there is no power on the monitor or keyboard. I don’t know what to check. This is a recent fault, since the pc worked fine for months. Please help if you can. I am not sure what processor is installed, since the motherboard supports both Cyrix and Pentium III.
Thanks alot. Jako Alberts