PC re-boot problems

[blackfive]

Over the past couple of weeks my PC has started to re-boot itself for no apparent reason. It happened just now as I was scrolling through a debate on AB, the screen suddenly goes blank and the machine goes into re-boot! I have anti virus software which is updated weekly and a firewall installed. I also do regular (weekly) disc maintenance. I haven't changed or added anything recently so does anyone have any idea what could be causing this problem?

[Worker]

Could it be a power surge or break in supply?

[j2buttonsw]

It sounds like a hardware fault so the first thing I would do is replace the power supply unit: it is pretty cheap at �25 and very easy to fit unless you have a slim-line/mini PC or older Compaq/Dell case which requires a special PSU.