usually i can troubleshoot some of the PC problems, but this one really got me thinking... 2 weeks ago the computer was making this static sound then go louder and the Computer turns off, it did not turn back on so i had to wait a few mins, unplug it from the wall or turn the PSU switch Off and On again so it could start. This first happen when playing a one of my video games, then it happen while on the internet watching videos and surfing...first i thought it was a Heating problem so i check for that. No, no heating problem, CPU, MotherBoard, NorthBridge, all stay unnder 45C while working and the CPU drop down to around 15C at idle. The only i have seen at 60-70C is the Video Card but that's when i'm playing games, then it drops down to ~35C.
List of things i have done so far without any success.
Clean the dust off the case and Motherboard with compress air.
Added 2 120mm fans to the case. it's running 5 fans now (1 front, 2 side, 1 rear, 1 top) CPU, PSU and GPU have their own fans as well. (8 total?)
Clean off and replace the Thermal Paste on the CPU.
Replaced the PSU with a bigger one, (from 650w to a 750w)
Run Anti-virus (it checked out clean)
Replaced the Hard Drive
Installed a fresh copy of Windows 7 Ultimate 64bit and all drivers
Removed the Ram and try one stick at a time
Removed the sata connectors and place them on different ports
removed the Video Card and place it on another slot
Log-on in SAFE MODE & SAFE MODE with NETWORKING
Run Windows Memory Diagnostic (no errors where found)
as you can see, i have done a lot of things and it still restarting without any warning like when you hit the reset button
Operating System: Windows 7 Ultimate 64-bit
Motherboard Manufacturer: Gigabyte Technology Co., Ltd.
Motherboard Model: GA-990FXA-UD3
BIOS: Award Modular BIOS v6.00PG
Processor: AMD FX-4100 Quad-Core Processor (4 CPUs), ~3.6GHz
Memory: 8192MB RAM
Available OS Memory: 8190MB RAM
Page File: 2149MB used, 14226MB available
Windows Dir: C:\Windows
DirectX Version: DirectX 11
Card name: NVIDIA GeForce GTX 550 Ti
Chip type: GeForce GTX 550 Ti