Recently my PC has started to re-boot without warning. It appears as though there may be a power supply fault like swithing on and off. The power supply unit is the original at 250W however the rest of the PC has been upgrade a coouple of times from 450Mhz to 2400Mhz processor. I re-installed XP just in case it was a software problem but it did it again. What do we think, power or processor problem?