So with "scanner" you ddidn't mean a virus scanner, but a peripheral scanner / printer / fax / etc.? And when you try to install Civ4, this opens your scanner directory? That's ... odd.
I'd try to ask in the hardware forum.
If you haven't already, you could also try to disconnect the scanner, or to start the installation manually, or to check the peripherals in your system settings. But I'm just shooting into the blue here, I've never had a problem similar to yours.
