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I am dealing with an older PC with Windows XP. Someone recently selected "Load Optimized Defaults" from BIOS and now tiny little problems have emerged.

One of the problems is that the Ethernet NIC doesn't work anymore. It is a

Marvell Yukon Gigabit Ethernet 10/100/1000

So when Windows starts the device doesn't work (Device Failed to Start). If I manually uninstall it and select "Scan for hardware changes" it is detected and installed without a hitch.

Now, something I noticed. When the OS boots the IRQ is 11. After I "Scan for .." the IRQ becomes 20. If I reboot the IRQ becomes 11 again and so the NIC doesn't work anymore.

I am really not into hardware things so I don't know what's causing this (except some IRQ conflict). Still, the devices are all PnP so I'm not sure an IRQ conflict is even possible.

Thank you in advance for any suggestion.

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IRQ conflicts are possible with PnP detection. It's rare, but it happens. Try moving the NIC to a different PCI slot and see if that remedies the situation. – Breakthrough Aug 22 '11 at 18:42

Check your BIOS. Usually there is a setting "Plug and Play (PnP) OS." Usually that is off, thus BIOS sets up the devices. Try turning it on, which tells BIOS to let the OS set the PnP settings

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