new built system is dead

[needadvice]

I have some experience upgrading my computers with RAM, video cards or replacing floppy/ IDE hardrives and installing operating systems.
I am also knowledgable about POST, ESD discharges and the overall fonctionning of a PC but this is the first time I assembled a PC from scratch.

Following carefully all the manuals (case, cpu, psu, motherboard, video, RAM, floppy, HDD, CD-ROM, etc) I assembled my first Intel Pentium-IV PC.

Then (with the side panel off) I turned the system on for the first time: All the 4 fans (CPU, PSU, back and front fans) started spinning and the power led on the front of the case turned o but the video BIOS screen was not still on the monitor ( it was all black color).

At this precisely moment (not even the 30 seconds to complete POST had elapsed) I realized that the four-pin ATX 12V Power Connector was not connected into the motherboard. Because I knew from my motherboard' s manual than this avoid the system to boot up, I turn off the system immediately by pressing 3-5 seconds the power-on button on the front of the case.

With the system totally off and after I disconnect the PSU cable from the PC, I connected (using my anti static wrist band as alwas) the four-pin ATX 12V Power Connectoras indicated in the Mobo' s manual and tried to turn the system on again. But this time: No fans running, No power led on, No POST, no nothing.

My newly built system looks like dead with just one signal of life: the onboard LED of the Mobo lights up green color.

Could someone please give some advice on how to troubleshooting this problem? Your help will be greatly appreciated

[Hi Ho]

Pleas post your complete system specs including the brand and wattage rating of the power supply.

[shadowpr]

Try this: http://forum.pcmech.com/showthread.php?t=132409

Remember that the MB needs to be outside of the case.