PC shutsdown and restarts indefinitely while booting!

MonoColorado

Honorable
Aug 14, 2013
4
0
10,510
Hi, as the title says, I have this new PC I built which shutsdowns and restarts indefinitely after the BIOS.

This is the system I have:
■Mother: Gigabyte GA-Z87-HD3 ***
■RAM: DDR3 1600 Mhz (2x4Gb) Gskill Sniper CL9 1.25v
■HDD: 1 Tb WD SATA III Blue 64Mb Buffer
■Procesador: Intel Core I5 4430 Haswell
■PSU: Cooler Master Silent Pro 700W

*** When I assembled the PC, my brother bent some pins in the CPU socket, so I sent the mother to Gigabyte's RMA and they fixed the bent pins. But since it was bad handling of it, they won't replace it (yes, I'll forcechoke my brother sometime later when I fix this).

Once it was fixed I installed everything perfectly in one afternoon (W7, Office, antivirus, a couple games which I tested, etc). When my brother came to try the PC later, the problems started. He moved the PC under the desk and replugged everything else. Later that day the problems started:

The PC works well until after it boots without the VGA, only one memory stick and no HDD or DVDD attached.
When either the DVD Drive or the HDD is plugged to the mother and PSU, the PC works well for some time the first boot (but not enough to log in Windows 7) but then just shutdowns and reboots (after like 5 secs) in a loop.

Is it the motherboard, PSU or CPU? I don't have another PSU to try.
I'd like to know if it's the mother so I just recycle this one and get a new one.

Thank you all in advance!