PC shuts down... and restarts

[chrismox]

I have an old PC that I was hoping to turn into a media centre, based upon an Abit NF7-S 2.0 motherboard.

It has developed a problem whereby when I ask it to shut down, it successfully does so, only to boot itself back up again rather than turning the power off.

It is subtly different than if I had asked the thing to restart as the power goes off for a brief moment before restarting, rather than remaining on as it would do when actually requesting a restart.

I have updated the BIOS, cleared the CMOS and set everything up correctly (I believe) but with no success.

Any ideas?

Thanks.

 

[furnace]

Have you tried taking out all expansion cards and seeing if it turns off properly then?

 

[chrismox]

Yep, the only thing in there is the graphics card.

I've also tried unplugging the network cable and that didn't help.

Is there any possibility that the CMOS battery could be the culprit?