PC continusouly shutdown before Drive detection on boot

Hello,
I'm having problem with unexpected shutdown after replacing my PSU ,graphic card and OS hard drive.

PSU: (Previous) Gigabyte 750W; (New) CoolerMaster 1000w
Graphic Card: (Previous) ATI Radeon 5850; (New) Geforce GTX 670
Hard Disk: (Previous) 1 TB Hitachi; (New) WB Veloci Rator 500GB

On Day1 and Day2 PC run with no issues. I was able to reinstalled windows 7 and all my software.

On Day3 after about 5-6 hours, my PC just shutdown with no warning. Then, when I tried to turn it on, it shutdown after displaying motherboard and CPU info but right before it shows the usual list of all detected drives.
Things that I did:
1. Replugged everything (PSU cable, Power cable, hard disks, Graphic Card but nothing.
2. Disconnected all my drives and tried to power on.
3. Testing RAM Card one by one
4. Reinstalling all my old hardware (graphic card, Power Supply) without hard disk connected.
All failed with a shutdown right before drives detection.
(CPU heat-sink is not hot at all and I never overclocked my hardware as a rule.)

Then I was away for about 20 minutes, when I came back and tried to boot, it was able to go past the drives detection but since no hard disk was connected, it shows the "Disk Boot Failure" Message.
Afterward, I switched back to the new Hardware Set, PC shutdown as before, then switched back to previous Hardware Set but still shutdown.

Eventually, I swapped to the new Hardware Set and replugged all my Hard Drives and decided to wait for the following day to try to turn it on. AND IT DID.
Run for about 6 hours without Issues (was able to run a game, download a couple of updates, play a movie) before it shutdown on me again. Same shutdown before drive detection problem.

Can anyone tell me what type on problem this is please, do I need to change CPU or motherboard ...?