My computer randomly shut down and turn back on?

I was all ready to blame the PSU - don't know the Acbel name, but if it's this one:

http://www.acbel.com/PDF/P_PC/PS2_450W_i.PDF

Then the claimed specifications are pretty decent.

One very basic check, feel for any airflow from the back of the PSU, as fan failure can give random shutdowns if there is just enough passive circulation to keep it from cooking.

If it feels warm but with no movement, then it could be a fan failure. Take the side panel off and shine a light on the fan, even at idle, the fan in any PSU except a "semi-fanless" should be turning.

NB. The fan on a PSU is not intended to be user replaceable, though if reasonably competent (there may be mains voltage charge remaining on some capacitors, even when disconnected), it is possible to replace.

Windows key + Pause/break key

Advanced System Settings

Startup and Recovery

Settings button

Uncheck the box that says Automatic Restart

Then you may see a blue screen with the Stop Code like 0x000000c0 after the system failure instead of it rebooting.

In XP the drill down is a little different but find Startup and Recovery and uncheck the Automatic Restart.

Then post the Stop Code info or search it for a solution

Acbel is quite a expensive power supply.

I suspect your graphic card is the root cause.

Below it the specs for GeForce 9800GTX+ graphic card.

Thermal and Power Specs:

Maximum GPU Temperature (in C) 105C C

Maximum Graphics Card Power (W) 140W W

Minimum System Power Requirement (W) 450W W

Supplementary Power Connectors 6-pin x2

U should get a higher power supply such as 550W ....

http://blog.diyersitzone.net/

I had the same problem once. It's probably overheating; chances are your CPU fan's flooded with sand. Clean it up - that should fix it.

If it still doesn't work, it could have something to do with your computer's power supply.

Maybe your computer is over heating.. look for the processor fan ..is it in optimum performance and the processor and system temperature in normal operation.. or you have some hardware malfunction. re plug the hardware.. and maybe you could monitoring temperature in the bios and wait.

i am damn sure it related to heating open up your cpu and clean dust on the fan above the hardisk :) if this doesnt help then call your PC engineer and tell him you might want to get a extra fan inside the cpu :)

That happened to me but it wasn't my computer. It was my TV..It got stuck by lightning and I had to put up with it or get a new one..GOOD LUCK whatever it is..Hope it's not from lightning.

Possibly over-heating ?