Why does my computer keep shutting down all by itself?

Q I have a Packard Bell PC that is at least four years old. It is running on Windows XP and, until recently, I have not experienced any major issues with the computer.

Recently though, the PC has begun powering down of its own accord. Even once it has shut down, a cooling fan on the motherboard continues to spin.

I took the side panel off the PC to see if the problem had an obvious answer, but everything seems to look all right (for a complete novice, that is). Can you help at all?
Tony Crowe

A This sounds like a classic case of overheating. If components inside the computer get too hot, they can become unreliable or even be permanently damaged.

Because of this, the insides of modern PCs are littered with temperature sensors, which constantly monitor heat, both of specific components and the overall warmth inside the case.

If a particular component – typically the processor – reaches a critical temperature, then the PC’s Bios may be configured to automatically shut down the computer to prevent damage.

At the same time, the computer’s circuitry may be rigged in such a way that one or more fans will continue spinning for a short time after the computer itself is switched off, to reduce the heat.

The symptoms you describe clearly point to overheating as the reason for the automatic shutdowns – though obviously this is distinct from the root cause of the problem.

To diagnose what is behind this, begin by accessing the computer’s Bios: this is usually achieved by tapping the F2 or Delete (Del) keys on the keyboard shortly after the computer is switched on.

When the Bios page appears, navigate through its menus and tabs using the arrow (cursor) keys and Enter. Look for a Hardware Monitor section, which might be under the Power tab. From here, you should be able to see the heat readings from all the temperature sensors inside the PC.

Alternatively, by installing a free utility such as Speedfan, you will be able to read the computer’s thermometers from within Windows.

Download Speedfan from Almico's website and see Computeractive's workshop explaining how to use Speedfan for help.

Either way, you should now be able to keep an eye on the temperature of at least the processor (or CPU, as it may be labelled in the Bios). We don’t know what processor is inside your PC but the maximum safe operating temperature for modern chips varies greatly – some can safely tick over at 90˚C while others are at risk of conking out at much lower temperatures.

Ditto other components, such as the graphics card’s processor. Regardless, if the computer’s shutting down seems to coincide with excessive heat readings from one or more of the temperature sensors then you will be on the way to identifying the cause.

You could also try running the PC with the side of the case removed to see if this reduces the temperature and resolves the problem, though this is obviously dangerous and certainly not recommended as a long-term fix.

A common reason for PCs getting excessively hot is that their fans are either faulty or not working efficiently. As you have already looked inside the case and confirmed that the fan seems to be spinning, then a good clean may help improve its efficiency.

Wearing an anti-static wrist strap, use a can of compressed air to blow dust away from the fan blades and, if necessary, use a cotton bud to carefully remove other gunge. Also, the speed of some fans can be regulated, sometimes manually though mostly through software – again the Bios settings or Speedfan should be able to help here.

Finally, if all else fails, a trip to the repair shop may be required. While replacing the fan or even the processor may be possible, it certainly isn’t a job we would advise for novices.