First of all, I apologize if there's any other topic equal to this one, but I couldn't solve my problem anyway.
Sorry for my writing too. English is not my native language.
Well, I built a PC with the following specs (none of its parts are used):
Motherboard: Gigabyte GA-H61M-D2-B3;
CPU: i3 3320 (Ivy Bridge);
RAM: Kingston 4Gb;
PSU: CoolerMaster Elite Power 400W.
I think I plugged everything in the right place.
When I turn on the PC, the CPU sometimes beeps, but I usually hear nothing. Anyway, nothing appears on the screen and it turns off after exactly 10 seconds. Some seconds later, it turns on again by itself and restarts this cycle (turns off, turns on....), which only stops when I unplug it. This happens either if everything is plugged (HD, DVD, additional cooler, etc.) or if only the CPU, RAM and energy cables are plugged.
I've reseated the cables, the CPU and the cooler, but it doesn't solve the problem. I already tested the PSU in another PC (a Sempron), and it turned on without any problem. Unfortunately I haven't had the opportunity to test the motherboard, the CPU or the RAM in another PC yet.
An information that may be useful is that, if I'm not mistaken, the BIOS version isn't the latest one, so I think the mobo doesn't support the CPU since it's an Ivy Bridge. Nonetheless, in this case, would this problem be a normal "symptom"?
One more thing (it's probably useless, but I think it's not a problem to leave it here): When the PC turns on, I hear that "PC-turning-on little noise" (you know, every PC does that almost inaudible sound - not talking about the beep), but sometimes I hear it twice in a very short period of time (less than one second), just like it's turning off and on again. I don't know if it means something though.