Yeah, as per the title, i'll just be running the computer normally when it'll just turn off, like someone turned the power off. And it seems to happen without fail if i run anything graphical, like a game. Running + Specs: Windows XP Prof SP3 AMD Athlon 2700+ 1.5Gb RAM NVIDIA GeForce 6200. i've tried virus and spyware chekcs registry cleans, defrags, but nothing seems to help.
This sounds like the overheating auto-shutdown mechanism that kicked in. If it was malware or something like that.. then you would see Windows actually shutting down properly. Get an air can and cotton on a stick (Q-tip's), remove all fans, and clean the heat sink properly. Use the Q-tip's to gently remove dust from the fan blades. Then turn on your computer, while having the case CLOSED, with a program that monitors temperature, and see what's going on. If the problem is due to the CPU, probably the CPU was miss attached and created a air bubble in the layout of the thermal paste. Remove the CPU heatsink, remove the old layer of thermal paste, and apply a new one with high quality thermal paste. A thin layer is all you need. If the temperature are normal, and it still occurs, try a different program to confirm the problem. If you can see anything wrong, then the problem might be the power bar. Ensure that the power bar does not shut-down other devices while this problem on your desktop occurs. If the Power bar is not the problem, then it is with the PSU. See if your PSU is under warranty for replacement, if not, then it's time for a new PSU. Look for brands like Corsair which offers 5 year warranty on the PSU, and are also efficient, and provide a more stable current to your components inside your computer. My recommendation for a software to monitor your hardware is sadly not free, it's Lavalys Everest. This tool also provide a system stability test, so you can stress your computer to make sure everything is fine.
check the windows event log for any system errors (bluescreens) Alternatively in control panel -> system -> advanced -> startup & recovery, disable automatic reboot on bluescreen. Quite often bluescreens disappear so quickly it looks like just a reboot.
No, its not a bluescreen, and the auto-reboot is off. It was an overheating problem, so it got a full clean and a fresh layer of themal compound, plus a PCI fan unit. So its working great now. Thanks for the help guys