gistfile1.txt

# variables
$url = "http://packages.nuget.org/v1/Package/Download/Chocolatey/0.9.8.4"
$chocTempDir = Join-Path $env:TEMP "chocolatey"
$tempDir = Join-Path $chocTempDir "chocInstall"
if (![System.IO.Directory]::Exists($tempDir)) {[System.IO.Directory]::CreateDirectory($tempDir)}
$file = Join-Path $tempDir "chocolatey.zip"

# download the package
Write-Host "Downloading $url to $file"
$downloader = new-object System.Net.WebClient
if (!$downloader.Proxy.IsBypassed($url))
{
    $cred = get-credential
    $webclient = new-object System.Net.WebClient
    $proxyaddress = $webclient.Proxy.GetProxy($url).Authority
    Write-host "Using this proxyserver: " $proxyaddress
    $proxy = New-Object System.Net.WebProxy($proxyaddress)
    $proxy.credentials = $cred.GetNetworkCredential();
    $downloader.proxy = $proxy
}
$downloader.DownloadFile($url, $file)

# unzip the package
Write-Host "Extracting $file to $destination..."
$shellApplication = new-object -com shell.application
$zipPackage = $shellApplication.NameSpace($file)
$destinationFolder = $shellApplication.NameSpace($tempDir)
$destinationFolder.CopyHere($zipPackage.Items(),0x10)

Line 14.... does this work without "http://10.6.76.20:8080" ?

It now has no more reference to the server. It should just pick it up if you have it configured. I hope this works for NTML proxies too but not sure.