Hi CLONNEN, there are several things that can cause no response from a computer, but finding which one is causing the problem is very tricky. First check that there isn't a fuse in the power supply. If there isn't, you could strip the computer down leaving only the motherboard with the processor and it's heatsink, the power supply the power switch and the case speaker connected. If there's still no sign of life, then you know the cause is one of those remaining items. Alternatively you could initially just fit a new power supply as the most likely to be the cause of the problem. Before you try this though, open the case, disconnect the power switch connector from the motherboard and short the motherboard power switch pins together. If this causes the computer to power up, then you will know that it's just the power switch that has failed.