Just noticed that the lights for the network port are on (both of them) when the power is connected to the system, but as soon as the case switch is switched on the lights go off. Interesting.

No keyboard lights means that POST isn't running. POST is the power on self test where the computer tests the keyboard and video.

Is this a new build or a store bought PC? Added any hardware recently?

Make sure that the power cable is firmly plugged in. Press it as hard as you can, sometimes they require a lot of force.

Also you may want to remove the CMOS battery to reset the hardware info. Open up the case after you disconnect all cables. Hold the power button to drain the power. Take out the large, round battery on the board. It has a clip near it to release it.

Take it out and put it to one side. Pop it back in after ten minutes and see if that helps.

PS if this happened after adding a new graphics card, remove it and use onboard if possible. Some graphics card cause this problem but you can turn the PC on after about 10 or 15 minutes

Amtech,

Thanks for this. I have just put in a new graphics card and the same problem occurs. I actually also discovered the power cable going into the back of the machine was faulty so have replaced that. Sadly it didn't fix the first problem but was throwing up a good red Herring.

I'm taking the battery out now for ten minutes...

Removing the battery didn't seem to work. I'll do some Googling around POST not running/failure.

I took the system right back to barebones and even tried to force it to give me some beep codes -- nothing. I think the motherboard is dead. Am going to try a new motherboard tomorrow :-(

Do the fans spin?

You should at least have the soft power light on on your motherboard. It lights up to let you know it is getting and storing power properly.

I think your power supply has probably died. Are you sure it was just the lead? If you use the power lead to power something else (like a kettle maybe) does it work then?

Basically you are not getting power to the motherboard or at least not enough power. I would try another power supply, perhaps a higher spec one such as 500W or 600W.

It could be that your new card is using too much power also. Try to stick in an older card or use onboard video if possible. If the problem happened at the time you replaced the card then hopefully its fixable by just using a lower spec card which in turn uses less power and should then allow you to power up all the components.

FYI there is a thing called a POST card which you plug into your PC and it displays error codes and text telling you why POST has failed. These are expensive though and I have never had the need to use them.

I think the issue here is more to do with the power supply than POST not running.