Why does my laptop power on again after shutting it down?

Hi,

I've got a laptop (HP 2307TX)which, when the AC Adapter is connected, will shutdown but 4/5 seconds later it will power on again!  Without the AC Adapter (battery only) it can shutdown fine, but if you plug the AC adapter back in again it will power on by itself.

Have latest BIOS, Vista is fully patched (SP2+hotfixes).  Booted into safe mode and then tested shutdown behaviour, same result.  CMOS Battery is reading 3.1V (using a DMM).
createcomsAsked:
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rhandelsCommented:
I've seen this behaviour when the machine is enabled for Wake on LAN.. Try disabling this feature within the Bios and check to see if it works..
This isn;t a Vista issue btw, looks like your laptop is triggered to startuip again after the shutdown..
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John GriffithConsultantCommented:
Go into power options and "reset to defaults"
START | power

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createcomsAuthor Commented:
Wake On Lan has been disabled, this had no effect to the issue at hand.
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rhandelsCommented:
Not quite sure if there is some sort of setting in the BIOS that enables to machine to autostart when connected to the power cable. I do know servers that have this kind of behaviour but you can disable it by using the BIOS, it might be worth a shot.. Else i'd suggest looking for other Wake On events in the BIOS, might be a wake on power supply or somethign like that..
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createcomsAuthor Commented:
The BIOS itself has no wake on lan options, those found in Vista have been disabled in light of this issue already (and as I said, no change)
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rhandelsCommented:
Hey,

But as said, it isn;t Vista that's booting up the machine. Vista isn;t able to start up the machine, this can only be done by the laptop itself.. That's why i stated to try and look into the BIOS. WHen you shut it down and remove the power cable it will still be shutted down, rigth?? If you insert the power cable it will start up right?? Imho this has got nothing to do with how your Vista is set up.. It looks like the laptop gets a signal from somewhere to start booting.. And as far as my knowledge of Vista goes, it isn;t able to also..
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createcomsAuthor Commented:
Whilst it is true that Vista cannot boot the machine, I wonder if the matter is related to the ACPI state - G2/S5 is probably what it finds itself in after being told by Vista to shutdown and because of that there is scope for both BIOS and OS to have left devices in a particular state (e.g. the WOL settings mentioned already).  

Further evidence to this is that, when the computer starts booting after I try to shut it down - holding the power button for 4 seconds will shut it down manually and keep it off, so it must be forcing it to the G3 state.  It's also interesting this amount if time is identical to the delay between OS-stimulated shutdown and the unprovoked power-on
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createcomsAuthor Commented:
BTW Sleep mode has been possible, so this further disproves the WOL antagonist theory.
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createcomsAuthor Commented:
I tried something overnight which I've been testing before posting.  It seems I've fixed the problem by shutting down the laptop and removing it's operating battery (not the RTC batt).  It sat like this overnight.  I reinserted the battery this morning and now I'm able to have AC Power connected and shutdown successfully, I'm able to shutdown in battery mode and connect AC Power without inadvertently turning it back on.

I would say in light of that fix, that the OS is not the bad actor at all in the equation - this is possibly a race condition in the HP ACPI core firmware/hardware?

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rhandelsCommented:
To be honest I never thought that removing the RTC battery actually solved this issue... It might be that HP has a problem with this, but still it's a very strange issue..
You might be able to contact HP and ask them about this?? They normally have quite a good support, i also have a few HP laptops at home..
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createcomsAuthor Commented:
No I said it wasn't the RTC battery it was the operation battery (or whatever you call THE battery which is being used when the AC switchmode isn't plugged in).  I did contact HP and no reply, they obviously don't care....
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