Hi there,
not exactly sure what 00 means on the LCD but I have a nagging feeling that I have read it means that everything is basically OK with the system.
When you say the PC isn't running do you mean you are not getting anything showing on the monitor or that none of the fans are running?
If it's that you are not getting anything showing on the monitor, have you another GPU to try? Have you connected any extra power leads to the GPU if needed? Have you checked the monitor power lead and the video cable are connected properly.
If it's that you are not getting any power to the fans etc the check that you have connected all the power leads to the motherboard. Also check that you do not have an electrical short that can cause similar problems.
Try going back to the very basic components CPU, cooler, GPU and one stick of RAM and see if that gets the PC running.