I had a working i7 system that was10 yrs old. all of a sudden it died. Now if the power is plugged in I can see 2 lights on motherboard but start button does nothing. If disconnect power and connect after a few mins, press the start button then it starts momentarily with fans moving but only for about a second and then dies again. I have checked the cpu fans and they actually momentarily spin on start. I have taken out graphics card and tried but to no avail. I think the power supply is ok as it appears to be powering the sytem (with the 2 LED lights and the momentary start). I have also cleaned out all dust etc.