computer keeps shutting off

[towncarblue]

i have a E-machine minitower. when i turn on the PC , windows loads up as well as some other programs , then all of a sudden it shuts off and restarts (as if someone just cut off the power) , the pc does this over and over. i tried to reboot the pc but the same thing keeps happening? what could be wrong ? do i have to replace anything?
HELP ME

[Paleo Pete]

Spontaneous reboots are usually related to either excessive heat or a weak power supply.

Open the case and blow out all the dust with some canned compressed air available at department stores or office supply retailers. Leave the side cover off and run it with a small fan blowing inside, and if it's in a cubbyhole on the side of a desk, get it out of there for troubleshooting. Lack of air circulation can and will cause heat problems. When cleaning out dust pay close attention to the fins of the heatsink and the fan or heatsink on the video card if it has one.

If heat turns out not to be the problem, see if you can get a known working power supply to test it with.

Sometimes it turns out software is causing the problem, but that's not often, it's heat or power supply 90% of the time.

[Whyzman]

Also, if you can get into the BIOS most motherboards are equipped with a thermistor that reports temps under one of the headings in there. You could keep an eye on it and see if the temps get out of sorts...

This approach might be beneficial especially if it is rebooting while merely idling...