Give us a rundown of your entire system specs, including heatsinks, fans, and power supply.
Try unhooking all hardware except what is necessary (CPU, memory, video). Add in each component after a successful boot. This way you can isolate what is causing the problem.
Also, look through every BIOS option and make sure it's correct. Load fail-safe defaults and start over if you are unsure which option to select.
Usually hardlocking or random shutdowns are related to heat or power. I am eyeing one of these components. However, I am not ruling out anything yet, even a possible faulty software installation if the problem occurs in the same place every time.