I have a Gateway Desktop with a Phenom quad core processor and 4 GB RAM, and I have added an ATI HD 4850 graphics card to it. This combination has run very well for me, over a year, until recently, when I am playing Fallout: NV the system just shuts off, no warning. The LED in the power button stays lit, but everything is shut down. What I don't know is if it is a thermal issue with the CPU or if the power supply is failing. The fan is running on the graphics card, and on the CPU, so I'm leaning more towards the power supply being the issue.
Also, possibly related, when I shut the computer down and leave it off for a few days, when I start it up, it jumps to the BIOS screen to enter the correct date/time before it will run. Could the backup battery be an issue? I don't unplug the box or anything crazy, just a normal shut down in Windows (Vista, BTW)
Any ideas? I really can't afford to just throw parts at it right now, so any help would be greatly appreciated!