This may not be a dead machines problem so pardon me if it's not
My brother has a home built machine running Windows Vista RC1 and this problem has only started since having this particular OS installed.
He can power it off ok through the usual resources of telling the OS to shut down etc, however after about 5 to 10 minutes the machine will power itself back on without any user intervention. He has so far got around the problem by turning off his PSU at the rocker switch but he is getting tired of turning the machine on and off from the back of the system all the time.
I doubt this is a hardware issue in itself but it is possible I suppose so I'm generally looking for a 2nd opinion.
In the BIOS of this particular machine (award- phoenix) I have noticed a Rocker switch function with the options of 'break/wake' and disable. It is currently set to the first option of break/wake. I think this is part of the problem but am uncertain as I seem to recall that a problem was reported to Microsoft about Vista RC1 turning machines on if they had Rocker Switches.
Any light would be greatly appreciated. Thanks:)