I'm having some problems with a PC not booting. About 2/3rds of the time I try to boot, it gets past the post beep but before the Windows splash screen displays, it just shuts off. No error message or anything, the power just cuts off. It may be worth mentioning that every attempt to enter the BIOS setup has resulted in it suddenly shutting off too. Also, once it does boot up after a couple tries, it runs fine and stays up until I choose to shut it down.
I'm not an expert with computers, but a co-worker suggested it was either a problem with the power supply or it's overheating. On one of the rare times it booted up fine I installed SpeedFan and it shows the following:
63c load is very good for a 8800ultra but idle well that isn't the worst that I have seen. Does this rig crash during gaming? I would also assume that the psu may be at fault. Overall the temps are good so it is not the cards at least thermal wise.
Try plugging your monitor into the integrated video card on your motherboard...if it still shuts down then it is not your GPU if it doesn't then i'm guessing its your CPU. For most CPUs temps above 60C or 65C are high and the computer will most likely shut down. What are you using to cool your CPU? Make sure that the liquid cooling block is making direct contact with the CPU itself, and also make sure that the pump or fan of your liquid cooling system is running.
I'm going through a number of troubleshooting ideas offered here and from a post to another forum. While I'm doing all of that I noticed another symptom that might be worth passing along -- when I attempt to reboot, it instead shuts down. And whenever I attempt to access BIOS it immediately shuts down and the next time I boot I get the following message: "CMOS checksum error - defaults loaded."
Usually when that pops up there is an issue with the bios losing saved settings due to bad battery that is used to maintain a small source of power. The battery can be bought just about any where. 3v lithium button cell. Beyond that any thing else that can cause that is if the system is unstable if it was overclocked.
this may seem off but could there be a short within the power supply, my father had a similar problem, but not dealing with such complex system, just an old dell tower, the enviroment within the tower would get just warm enough and had maybe a few to many dust particles that a small short within the main power circuts would trip the outlet breaker (not the fuse box, just those little buttons on the outlet that cut some power) resulting in the cpu not getting the juice it needed and imediatly shutting off.