Unplug everything except 1 DIMM RAM, CPU/Fan and video card. Everything else including hard drives, optical drives, case fans, floppy, etc. Boot into BIOS and let the system run. If the system shuts down, the MB may be shorting out to the case. Try properly reinstalling the MB. be sure to use the brass risers which normally come with the case. Other things that could cause the system to short out like it is doing. PSU. Bad SATA/IDE cables. I have the same MB.