Loss of power

My Desktop seems to suddenly switch itself off on occasions. It can work perfectly fine for ages and suddenly taking fits of conking out and starting again. Any suggestions would be gratefully accepted

Overheating. How dusty is it inside? Maybe a fan is failing intermittently.

As per aircobra, can also be the PSU and I have seen the exact same recently with faulty BIOS and memory combination. I would start my checking for faulty fans and dust build up. After that you are just throwing money at the problem which may not fix it. Also try googleing for the problem with you make/model of pc, you might get lucky! and find it is a common fault.

Of course this is a standard feature of Vista, which likes to automatically reboot to install updates with very little warning :-(((

:-(((