I just wanted to join this site and share my recent issue and troubleshooting that led to fixing my computer. I really wish I could have found the real problem first, but thought this could help some of you!
My initial setup, built in 2009:
MB: ASUS M4A78-E AM2+/AM3 AMD 790GX HDMI ATX AMD Motherboard
CPU: AMD Phenom II X4 945 Deneb 3.0GHz Socket AM3 95W Quad-Core Processor
Memory: 4 x G.SKILL (2GB) 240-Pin DDR2 SDRAM DDR2 1066 (PC2 8500) Dual Channel Kit Desktop Memory
Video Card: VisionTek 900244 Radeon HD 4870 512MB 256-bit GDDR5 PCI Express 2.0 x16 HDCP Ready CrossFireX Support Video Card
Power Supply: CORSAIR TX Series CMPSU-750TX 750W ATX12V v2.3 SLI Ready CrossFire Ready 80 PLUS BRONZE Certified Active PFC Compatible
Problem: While watching a DVD, the screen suddenly froze. I thought it has somehow paused, but the mouse and keyboard were unresponsive. So, I powered it down, and rebooted. However, when rebooting, it would only get to the windows icon, then freeze. After another reboot,, it wouldn't display anything. The fans would spin, but nothing would be displayed to the monitor.
I'm not the best at troubleshooting, but my first thought was video card. I plugged into on-board video, and same thing. No video signal.
Video card ruled out.
So, I pulled the memory, and rebooted with one stick. This time i was able to view the bios, so I quickly reviewed the hardware monitor. All temps and voltage were normal. The CPU and memory were recognized, meaning their details were properly displayed in bios. Upon a complete reboot though, every time the boot went pass the bios prompt, it would restart.
So, I'm pretty much stumped at this point. All I can think to do is start ordering parts,, which I really don't want to do. I had my hard drive scanned at my college lab. No viruses, or vaults.
Hard drive ruled out.
I thought the problem was the motherboard for sure. I ended up ordering an open box motherboard and some new G-skill DDR3 memory. Replaced both upon arrival, and now I was able to view the bios again, upon every startup. However,,,, SAME issue. Once past bios, automatically restarts. Sometimes it would be hung-up for a couple minutes without displaying anything.
Now here is where I should have been smart, and suspected the CPU before the power supply. I ended up replacing the power supply since they seemed to fail more often then CPU's. However, new power supply, same issue.
Power supply ruled out.
Finally, after realizing I'm no hardware professional (as I have replaced everything but the actual failed hardware component), I finally ordered a replacement CPU. With a new CPU installed,, it is FINALLY WORKING!!!
This may or may not help you in troubleshooting your own issue, but I'm sure someone out there will find this useful. I did do research before hand, and most of what I researched pointed towards the motherboard and power supply.
Good luck to anyone out there with the same issue!