By the way, the processor is AMD Phenom II X4 805 quad core. 8 GB DDR2 system RAM.
I have a two year-old Gateway DX4300-11. Windows 7 Home Premium with all updates. Norton 360. I added a Sapphire AMD HD5400 PCIe X16 video card. PC is otherwise as purchased.
PC will occasionally appear to hibernate, even though power settings are set to never hibernate. Power switch light is on. Power supply fan is running. I can open CD/DVD drive drawer. However, nothing I have tried will wake the PC up. Pushing/holding the power button has no effect. Cannot even shut down PC with power button. Only solution I've found is to uplug cord from back of power supply. When I plug back in, PC restarts automatically without pushing power button.
Problem seemed to start about a month ago after I started using dual monitor function with plasma HDTV hooked up to HDMI output and PC monitor hooked to DVI output as primary monitor.
Thought perhaps this over-stressed the video card so I disconnected HDTV and connected monitor back to HDMI output. No good so I replaced the video card. Still have the problem. I have run software and hardware diagnostics from FixIt Utilities and Advanced SystemCare as well as hardware stress test utilities. No problems have been found.
Is it possible to find the issue in the event log? I'm wondering now if I should replace the power supply but would prefer to successfully troubleshoot first.