I have a HP Pavillion model a404x that runs windows xp. I can not get the computer to turn on. On the front, the power button flashes with a light blue light. In the back, there is a round bright green light that flashes. It is like it is in standby mode. When I unplug the computer, it flashes for a while longer like there is an internal power source. please help.
Moved your thread to Gen. Hardware Pappoose. This does sound like a hardware fault.
Do the fans spin up at all when you try to turn on the machine?
The flashing light on the back is the LAN (internet connection), the light coming on faintly on the front meant the power switch on the front is probably good, but most likely the PSU (power supply) is bad.
You can either swap the power supply out of that machine with another to see if thats the problem or you can just get another and hope that fixes it.
That PC is really old and doesn’t require an expensive PSU, so this one looks like a good way to go: XIGMATEK ACXTNRP-PC402 400W $35