|If it is an overheating problem, your processor may already be damaged. Try cleaning it up, as suggested, and be particularly mindful of the dust in/on the processors heatsink. The better BIOSes will show the temperatures of hardware components (usually in the PC Health page), so try booting into the BIOS immediately after an unwanted shutdown/reboot. Post back with the temperature show for your processor (CPU), and someone here will be able to tell you whether or not it's at an acceptable level. Laptops are particularly susceptible to overheating due to dust build-up, but desktops are also at risk, more so when they are running in dusty environments, or are subjected to cigarette smoke (nicotine and tar residue tends to cause dust to collect faster, due to stickiness). As a moderate to heavy smoker, I have to clean my machines far more regularly than most (everything gets a sticky coating, that needs to be cleaned off). I've seen computers in very clean environments begin to overheat due to dust build-up, so don't feel ashamed if your machine proves to be quite dirty inside (unless it's happening often, like in my case,LOL).|
The same problem can also be caused by a failing/underpowered power supply. What is the output of your power supply? How many hard drives, DVD/CD drives, Add-on PCI/PCIe cards, external USB/firewire devices (without own power) are competing for power from your supply? You don't state whether this is a brand-name computer, or custom-built. Many brand-name machines come with low-output power supplies (300 Watt or less), and struggle to supply enough juice for any added cards/ USB devices/ drives, etc. Power supplies are relatively cheap, so get the highest output you can (be aware that some supplies have different plugs, for connecting to the motherboard, and some without connectors for SATA drives). Often, a borrowed PS (even a low-powered one) is a no-cost option for testing purposes (a low-powered PS may still output more than your current PS, due to yours having been over-worked for an extended period of time).
I would expect overheating to be the first thing to investigate, but if that doesn't help, let us know the output of your PS and the number of devices/cards/drives you are running.
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