Power Question

I have a Lenovo desktop Vista Business PC which recently had been sent out to a shop for a virus cleanup. It was wiped, new OS installed (upgraded to Vista Business from XP) and some user data was transferred from the previous install.

The users of the PC shut it down when it is not in use. After coming back from the shop, the users called me about an issue with the computer turning on by itself from a complete shutdown. I assumed it was asleep instead and woke up to run some task or other. However at this point I can confirm that the computer is being shut completely down, the power button on the case is completely dark, and within about 20 to 30 minutes it will power on by itself. I've not seen this before, and don't know what the possible causes might be. Anyone else have any ideas, or seen this before?
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Mark DamenERP System ManagerCommented:
Seen it before where the power supply if faulty.  Get this issue whereby it turns itself on randomly, and also where it won't turn on when requested.  I would suggest that testing a new PSU should fix your fault.

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First I would go in to the bios and disable wake on LAN.  Also check to see what the power settings are in the bios and see what “after powerloss: function is set to if it’s set to on even a small amount of power loss or fluctuation will cause it to power on.  However if it’s set to off then it should stay off.  I have noticed this lately with my laptop at work.  A small bump in power when they test the generator causes it to power on when they switch from generator back to regular power
Vista has a hybrid hibernate-shutdown as default.  with this setting, windows update or some other tasks will start up the pc and not shut it down.  Pressing the start button does not shutdown it goes into this mode by default.  To change this is a little confusing.  
check the power settings; CP\Power options\ChangePlan..\cchange advanced..  browse down to the power buttons setting and set the operation the way you want.  Hope this helps.  kevin
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you can test if it does it from battery, or AC alone
also - a bios update can help
I have seen this problem with a faulty power switch. I too thought it was a faulty power supply. You could try unplugging it (the switch) from the front panel header and see if the problem stops. Just trace the wires from the switch to the motherboard. Leave unplugged. If the switch is bad the PC should stay off.
westoneAuthor Commented:
Unfortunately EE site is forcing me to accept a suggestion that did not work so that I may use my account, when in reality the computer in question has not yet been available for me to test the most recent suggestions.
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