PC starts when connected to mains before pressing

  gourmand 11:18 23 Oct 2010

Hi, I just wondered if anyone has come across this before (I had a long time ago but can't remember what the cause was). A PC I have been asked to look at starts itself up as soon as the power lead is connected, after booting to the welcome screen then shuts down. Just thought I'd ask before getting to work with the phillip's it has an ASUS M2A-VM HDMI mainboard XP home.
Any help appreciated.

  onthelimit 11:21 23 Oct 2010

Could it be the on switch is stuck 'on' (or a short)? That would trigger the psu to kick in when connected. Then, as it booted up, the psu would get the message to shut down 'cos the switch is being held in.

  gourmand 11:23 23 Oct 2010

Makes sense, I'll check that out, thanks

  Taff™ 11:23 23 Oct 2010

Just a theory. If the power button on the computer is stuck or there is a short which means it is always on, the computer will power up as you describe. At the point where Windows Loads, If the computer has been set to "Shut Down when the Power Button is pressed" it will do just that!

  Taff™ 11:24 23 Oct 2010

Must type faster!

  Fruit Bat /\0/\ 11:30 23 Oct 2010

Signs of a failing PSU

However check the power saving options in BIOS

  onthelimit 12:14 23 Oct 2010

Not quite sure why a 'failing PSU' would start without the button being pressed?

  Jollyjohn 13:19 23 Oct 2010

In the BIOS there is usually a power setting labeled - AC resume after power loss - or similar. This can be set to always off, same state or always on.
Always on means the PC would reboot after a power cut.

A quick test to run would be to disconnect the power switch from the motherboard and connect the reset switch in it's place. If the PC behaves properly - the power switch is the culprit.

  Fruit Bat /\0/\ 14:32 23 Oct 2010

Had a couple of machines that started as soon as plugged into the wall and then the PSU has failed completely within a month or so.

  T0SH 17:02 23 Oct 2010

Enter BIOS setup and disabling "restart on power failure" will fix it for you

Cheers HC

  gourmand 17:56 23 Oct 2010

Sorry everyone what I was told was the problem was incorrect. I have set up the PC and what actually happens is that it does start up as soon as the power is connected, goes through to the windows startup screen then fails back to the "windows has failed due to a hardware change etc, please choose an option of normal startup, safe mode etc. whichever you choose the same loop occurs. I have tried all the suggestions above, even when both PWR and Reset are disconnected from the mobo it still fires up! I have disconnected dvd rom, changed the psu cleared the cmos etc to no avail. so I think it may well be the mobo itself.

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