Disable 'Automatically detect settings' in Internet Explorer's proxy settings dialog.

Disable-AutomaticallyDetectSettings.ps1

# Disable 'Automatically detect proxy settings' in Internet Explorer.
function Disable-AutomaticallyDetectProxySettings
{
    # Read connection settings from Internet Explorer.
    $regKeyPath = "HKCU:\SOFTWARE\Microsoft\Windows\CurrentVersion\Internet Settings\Connections\"
    $conSet = $(Get-ItemProperty $regKeyPath).DefaultConnectionSettings

    # Index into DefaultConnectionSettings where the relevant flag resides.
    $flagIndex = 8

    # Bit inside the relevant flag which indicates whether or not to enable automatically detect proxy settings.
    $autoProxyFlag = 8

    if ($($conSet[$flagIndex] -band $autoProxyFlag) -eq $autoProxyFlag)
    {
        # 'Automatically detect proxy settings' was enabled, adding one disables it.
        Write-Host "Disabling 'Automatically detect proxy settings'."
        $mask = -bnot $autoProxyFlag
        $conSet[$flagIndex] = $conSet[$flagIndex] -band $mask
        $conSet[4]++
        Set-ItemProperty -Path $regKeyPath -Name DefaultConnectionSettings -Value $conSet
    }
    
    $conSet = $(Get-ItemProperty $regKeyPath).DefaultConnectionSettings
    if ($($conSet[$flagIndex] -band $autoProxyFlag) -ne $autoProxyFlag)
    {
    	Write-Host "'Automatically detect proxy settings' is disabled."
    }
}