Startup problem or motherboard

First, this problem is due to another problem still valid before this problem but not the subject of this topic. So I opened my computer and remove (and given) the graphics card, the wireless card the small battery and usb ports. But when I turn on my computer, it turns 1 seconds and off (no noise). When I disconnect the supply port 8 pins located close to my processor, the computer stays on but does nothing. Do you know where it can come and if so, how to solve this problem.

My config: Motherboard: Asus P5N32-E SLI Processor: Intel Core 2 E6850, Graphics card: Nvidia 8800 Ultra, power supply 550 Watts.

Remove the battery only recover the default BIOS (CMOS Clear, useful in case of bad settings in the BIOS) but does not in any case to start normally.

The boot sequence may be wrong but it does not turn on the PC properly, it may just prevent the system to load if it is the bad hard drive defined. At first glance it looks like a PSU that cuts alone (live life or lack of power):